diff --git a/contracts/AllocatedCrowdsale.sol b/contracts/AllocatedCrowdsale.sol
index 76265c75..3e4b19e5 100644
--- a/contracts/AllocatedCrowdsale.sol
+++ b/contracts/AllocatedCrowdsale.sol
@@ -57,6 +57,6 @@ contract AllocatedCrowdsale is Crowdsale {
    * Use approve() given to this crowdsale to distribute the tokens.
    */
   function assignTokens(address receiver, uint tokenAmount) private {
-    if(!token.transferFrom(beneficiary, receiver, tokenAmount)) throw;
+    require(token.transferFrom(beneficiary, receiver, tokenAmount));
   }
 }
diff --git a/contracts/BonusFinalizeAgent.sol b/contracts/BonusFinalizeAgent.sol
index 4e2b06d8..fb8dcdaa 100644
--- a/contracts/BonusFinalizeAgent.sol
+++ b/contracts/BonusFinalizeAgent.sol
@@ -35,17 +35,11 @@ contract BonusFinalizeAgent is FinalizeAgent {
   uint public allocatedBonus;
 
   function BonusFinalizeAgent(CrowdsaleToken _token, Crowdsale _crowdsale, uint _bonusBasePoints, address _teamMultisig) {
+    require(address(_crowdsale) != 0);
+    require(address(_teamMultisig) != 0);
     token = _token;
     crowdsale = _crowdsale;
-    if(address(crowdsale) == 0) {
-      throw;
-    }
-
     teamMultisig = _teamMultisig;
-    if(address(teamMultisig) == 0) {
-      throw;
-    }
-
     bonusBasePoints = _bonusBasePoints;
   }
 
@@ -56,9 +50,7 @@ contract BonusFinalizeAgent is FinalizeAgent {
 
   /** Called once by crowdsale finalize() if the sale was success. */
   function finalizeCrowdsale() {
-    if(msg.sender != address(crowdsale)) {
-      throw;
-    }
+    require(msg.sender == address(crowdsale));
 
     // How many % of tokens the founders and others get
     uint tokensSold = crowdsale.tokensSold();
diff --git a/contracts/Crowdsale.sol b/contracts/Crowdsale.sol
index 8a42bf5d..3a5da440 100644
--- a/contracts/Crowdsale.sol
+++ b/contracts/Crowdsale.sol
@@ -127,6 +127,12 @@ contract Crowdsale is Haltable {
 
   function Crowdsale(address _token, PricingStrategy _pricingStrategy, address _multisigWallet, uint _start, uint _end, uint _minimumFundingGoal) {
 
+    require(_multisigWallet != 0);
+    require(_start != 0 && _end != 0);
+
+    // Don't mess the dates
+    require(_start < _end);
+
     owner = msg.sender;
 
     token = FractionalERC20(_token);
@@ -134,27 +140,10 @@ contract Crowdsale is Haltable {
     setPricingStrategy(_pricingStrategy);
 
     multisigWallet = _multisigWallet;
-    if(multisigWallet == 0) {
-        throw;
-    }
-
-    if(_start == 0) {
-        throw;
-    }
-
     startsAt = _start;
 
-    if(_end == 0) {
-        throw;
-    }
-
     endsAt = _end;
 
-    // Don't mess the dates
-    if(startsAt >= endsAt) {
-        throw;
-    }
-
     // Minimum funding goal can be zero
     minimumFundingGoal = _minimumFundingGoal;
   }
@@ -162,8 +151,7 @@ contract Crowdsale is Haltable {
   /**
    * Don't expect to just send in money and get tokens.
    */
-  function() payable {
-    throw;
+  function() {
   }
 
   /**
@@ -181,15 +169,13 @@ contract Crowdsale is Haltable {
     // Determine if it's a good time to accept investment from this participant
     if(getState() == State.PreFunding) {
       // Are we whitelisted for early deposit
-      if(!earlyParticipantWhitelist[receiver]) {
-        throw;
-      }
+      require(earlyParticipantWhitelist[receiver]);
     } else if(getState() == State.Funding) {
       // Retail participants can only come in when the crowdsale is running
       // pass
     } else {
       // Unwanted state
-      throw;
+      revert();
     }
 
     uint weiAmount = msg.value;
@@ -197,10 +183,7 @@ contract Crowdsale is Haltable {
     // Account presale sales separately, so that they do not count against pricing tranches
     uint tokenAmount = pricingStrategy.calculatePrice(weiAmount, weiRaised - presaleWeiRaised, tokensSold, msg.sender, token.decimals());
 
-    if(tokenAmount == 0) {
-      // Dust transaction
-      throw;
-    }
+    require(tokenAmount != 0); // Dust transaction
 
     if(investedAmountOf[receiver] == 0) {
        // A new investor
@@ -220,14 +203,12 @@ contract Crowdsale is Haltable {
     }
 
     // Check that we did not bust the cap
-    if(isBreakingCap(weiAmount, tokenAmount, weiRaised, tokensSold)) {
-      throw;
-    }
+    require(!isBreakingCap(weiAmount, tokenAmount, weiRaised, tokensSold));
 
     assignTokens(receiver, tokenAmount);
 
     // Pocket the money
-    if(!multisigWallet.send(weiAmount)) throw;
+    multisigWallet.transfer(weiAmount);
 
     // Tell us invest was success
     Invested(receiver, weiAmount, tokenAmount, customerId);
@@ -270,8 +251,8 @@ contract Crowdsale is Haltable {
    */
   function investWithSignedAddress(address addr, uint128 customerId, uint8 v, bytes32 r, bytes32 s) public payable {
      bytes32 hash = sha256(addr);
-     if (ecrecover(hash, v, r, s) != signerAddress) throw;
-     if(customerId == 0) throw;  // UUIDv4 sanity check
+     require(ecrecover(hash, v, r, s) == signerAddress);
+     require(customerId != 0);  // UUIDv4 sanity check
      investInternal(addr, customerId);
   }
 
@@ -279,8 +260,8 @@ contract Crowdsale is Haltable {
    * Track who is the customer making the payment so we can send thank you email.
    */
   function investWithCustomerId(address addr, uint128 customerId) public payable {
-    if(requiredSignedAddress) throw; // Crowdsale allows only server-side signed participants
-    if(customerId == 0) throw;  // UUIDv4 sanity check
+    require(!requiredSignedAddress); // Crowdsale allows only server-side signed participants
+    require(customerId != 0);  // UUIDv4 sanity check
     investInternal(addr, customerId);
   }
 
@@ -288,8 +269,8 @@ contract Crowdsale is Haltable {
    * Allow anonymous contributions to this crowdsale.
    */
   function invest(address addr) public payable {
-    if(requireCustomerId) throw; // Crowdsale needs to track participants for thank you email
-    if(requiredSignedAddress) throw; // Crowdsale allows only server-side signed participants
+    require(!requireCustomerId); // Crowdsale needs to track partipants for thank you email
+    require(!requiredSignedAddress); // Crowdsale allows only server-side signed participants
     investInternal(addr, 0);
   }
 
@@ -326,9 +307,7 @@ contract Crowdsale is Haltable {
   function finalize() public inState(State.Success) onlyOwner stopInEmergency {
 
     // Already finalized
-    if(finalized) {
-      throw;
-    }
+    require(!finalized);
 
     // Finalizing is optional. We only call it if we are given a finalizing agent.
     if(address(finalizeAgent) != 0) {
@@ -344,12 +323,10 @@ contract Crowdsale is Haltable {
    * Design choice: no state restrictions on setting this, so that we can fix fat finger mistakes.
    */
   function setFinalizeAgent(FinalizeAgent addr) onlyOwner {
-    finalizeAgent = addr;
 
     // Don't allow setting bad agent
-    if(!finalizeAgent.isFinalizeAgent()) {
-      throw;
-    }
+    require(addr.isFinalizeAgent());
+    finalizeAgent = addr;
   }
 
   /**
@@ -395,13 +372,8 @@ contract Crowdsale is Haltable {
    */
   function setEndsAt(uint time) onlyOwner {
 
-    if(now > time) {
-      throw; // Don't change past
-    }
-    
-    if(startsAt > time) {
-      throw; // Prevent human mistakes
-    }
+    require(now <= time); // Don't change past
+    require(time > startsAt); // Don't allow to end before we start
 
     endsAt = time;
     EndsAtChanged(endsAt);
@@ -413,12 +385,10 @@ contract Crowdsale is Haltable {
    * Design choice: no state restrictions on the set, so that we can fix fat finger mistakes.
    */
   function setPricingStrategy(PricingStrategy _pricingStrategy) onlyOwner {
-    pricingStrategy = _pricingStrategy;
 
     // Don't allow setting bad agent
-    if(!pricingStrategy.isPricingStrategy()) {
-      throw;
-    }
+    require(_pricingStrategy.isPricingStrategy());
+    pricingStrategy = _pricingStrategy;
   }
 
   /**
@@ -431,9 +401,7 @@ contract Crowdsale is Haltable {
   function setMultisig(address addr) public onlyOwner {
 
     // Change
-    if(investorCount > MAX_INVESTMENTS_BEFORE_MULTISIG_CHANGE) {
-      throw;
-    }
+    require(investorCount <= MAX_INVESTMENTS_BEFORE_MULTISIG_CHANGE);
 
     multisigWallet = addr;
   }
@@ -444,7 +412,7 @@ contract Crowdsale is Haltable {
    * The team can transfer the funds back on the smart contract in the case the minimum goal was not reached..
    */
   function loadRefund() public payable inState(State.Failure) {
-    if(msg.value == 0) throw;
+    require(msg.value != 0);
     loadedRefund = loadedRefund.plus(msg.value);
   }
 
@@ -456,11 +424,11 @@ contract Crowdsale is Haltable {
    */
   function refund() public inState(State.Refunding) {
     uint256 weiValue = investedAmountOf[msg.sender];
-    if (weiValue == 0) throw;
+    require(weiValue != 0);
     investedAmountOf[msg.sender] = 0;
     weiRefunded = weiRefunded.plus(weiValue);
     Refund(msg.sender, weiValue);
-    if (!msg.sender.send(weiValue)) throw;
+    msg.sender.transfer(weiValue);
   }
 
   /**
@@ -517,7 +485,7 @@ contract Crowdsale is Haltable {
 
   /** Modified allowing execution only if the crowdsale is currently running.  */
   modifier inState(State state) {
-    if(getState() != state) throw;
+    require(getState() == state);
     _;
   }
 
diff --git a/contracts/CrowdsaleToken.sol b/contracts/CrowdsaleToken.sol
index e370bbbc..a856e72a 100644
--- a/contracts/CrowdsaleToken.sol
+++ b/contracts/CrowdsaleToken.sol
@@ -47,6 +47,9 @@ contract CrowdsaleToken is ReleasableToken, MintableToken, UpgradeableToken {
   function CrowdsaleToken(string _name, string _symbol, uint _initialSupply, uint _decimals, bool _mintable)
     UpgradeableToken(msg.sender) {
 
+    // Cannot create a token without supply and no minting
+    require(_mintable || _initialSupply != 0);
+
     // Create any address, can be transferred
     // to team multisig via changeOwner(),
     // also remember to call setUpgradeMaster()
@@ -69,9 +72,6 @@ contract CrowdsaleToken is ReleasableToken, MintableToken, UpgradeableToken {
     // No more new supply allowed after the token creation
     if(!_mintable) {
       mintingFinished = true;
-      if(totalSupply == 0) {
-        throw; // Cannot create a token without supply and no minting
-      }
     }
   }
 
diff --git a/contracts/DefaultFinalizeAgent.sol b/contracts/DefaultFinalizeAgent.sol
index b5ea5588..c4880cc6 100644
--- a/contracts/DefaultFinalizeAgent.sol
+++ b/contracts/DefaultFinalizeAgent.sol
@@ -31,9 +31,7 @@ contract DefaultFinalizeAgent is FinalizeAgent {
 
   /** Called once by crowdsale finalize() if the sale was success. */
   function finalizeCrowdsale() public {
-    if(msg.sender != address(crowdsale)) {
-      throw;
-    }
+    require(msg.sender == address(crowdsale));
     token.releaseTokenTransfer();
   }
 
diff --git a/contracts/EthTranchePricing.sol b/contracts/EthTranchePricing.sol
index 9de60246..14ea6bc4 100644
--- a/contracts/EthTranchePricing.sol
+++ b/contracts/EthTranchePricing.sol
@@ -48,9 +48,7 @@ contract EthTranchePricing is PricingStrategy, Ownable {
   /// @param _tranches uint[] tranches Pairs of (start amount, price)
   function EthTranchePricing(uint[] _tranches) {
     // Need to have tuples, length check
-    if(_tranches.length % 2 == 1 || _tranches.length >= MAX_TRANCHES*2) {
-      throw;
-    }
+    require((_tranches.length % 2 == 0) && (_tranches.length <= MAX_TRANCHES*2));
 
     trancheCount = _tranches.length / 2;
 
@@ -61,22 +59,16 @@ contract EthTranchePricing is PricingStrategy, Ownable {
       tranches[i].price = _tranches[i*2+1];
 
       // No invalid steps
-      if((highestAmount != 0) && (tranches[i].amount <= highestAmount)) {
-        throw;
-      }
+      require((highestAmount == 0) || (tranches[i].amount > highestAmount));
 
       highestAmount = tranches[i].amount;
     }
 
     // We need to start from zero, otherwise we blow up our deployment
-    if(tranches[0].amount != 0) {
-      throw;
-    }
+    require(tranches[0].amount == 0);
 
     // Last tranche price must be zero, terminating the crowdale
-    if(tranches[trancheCount-1].price != 0) {
-      throw;
-    }
+    require(tranches[trancheCount-1].price == 0);
   }
 
   /// @dev This is invoked once for every pre-ICO address, set pricePerToken
@@ -161,8 +153,8 @@ contract EthTranchePricing is PricingStrategy, Ownable {
     return value.times(multiplier) / price;
   }
 
-  function() payable {
-    throw; // No money on this contract
+  function() {
+    // No money on this contract
   }
 
 }
diff --git a/contracts/ExtraFinalizeAgent.sol b/contracts/ExtraFinalizeAgent.sol
index 47fe5850..d3e58a8f 100644
--- a/contracts/ExtraFinalizeAgent.sol
+++ b/contracts/ExtraFinalizeAgent.sol
@@ -38,17 +38,13 @@ contract ExtraFinalizeAgent is FinalizeAgent {
   uint public accountedTokenSales;
 
   function ExtraFinalizeAgent(CrowdsaleToken _token, Crowdsale _crowdsale, uint _bonusBasePoints, address _teamMultisig, uint _accountedTokenSales) {
+    require(address(_crowdsale) != 0);
+    require(address(_teamMultisig) != 0);
+
     token = _token;
     crowdsale = _crowdsale;
 
-    if(address(crowdsale) == 0) {
-      throw;
-    }
-
     teamMultisig = _teamMultisig;
-    if(address(teamMultisig) == 0) {
-      throw;
-    }
 
     accountedTokenSales = _accountedTokenSales;
   }
@@ -60,9 +56,7 @@ contract ExtraFinalizeAgent is FinalizeAgent {
 
   /** Called once by crowdsale finalize() if the sale was success. */
   function finalizeCrowdsale() {
-    if(msg.sender != address(crowdsale)) {
-      throw;
-    }
+    require(msg.sender == address(crowdsale));
 
     // How many % of tokens the founders and others get
     uint tokensSold = crowdsale.tokensSold().minus(accountedTokenSales);
diff --git a/contracts/GnosisWallet.sol b/contracts/GnosisWallet.sol
index 647de7fc..daf5cfc0 100644
--- a/contracts/GnosisWallet.sol
+++ b/contracts/GnosisWallet.sol
@@ -36,59 +36,50 @@ contract MultiSigWallet {
     }
 
     modifier onlyWallet() {
-        if (msg.sender != address(this))
-            throw;
+        require(msg.sender == address(this));
         _;
     }
 
     modifier ownerDoesNotExist(address owner) {
-        if (isOwner[owner])
-            throw;
+        require(!isOwner[owner]);
         _;
     }
 
     modifier ownerExists(address owner) {
-        if (!isOwner[owner])
-            throw;
+        require(isOwner[owner]);
         _;
     }
 
     modifier transactionExists(uint transactionId) {
-        if (transactions[transactionId].destination == 0)
-            throw;
+        require(transactions[transactionId].destination != 0);
         _;
     }
 
     modifier confirmed(uint transactionId, address owner) {
-        if (!confirmations[transactionId][owner])
-            throw;
+        require(confirmations[transactionId][owner]);
         _;
     }
 
     modifier notConfirmed(uint transactionId, address owner) {
-        if (confirmations[transactionId][owner])
-            throw;
+        require(!confirmations[transactionId][owner]);
         _;
     }
 
     modifier notExecuted(uint transactionId) {
-        if (transactions[transactionId].executed)
-            throw;
+        require(!transactions[transactionId].executed);
         _;
     }
 
     modifier notNull(address _address) {
-        if (_address == 0)
-            throw;
+        require(_address != 0);
         _;
     }
 
     modifier validRequirement(uint ownerCount, uint _required) {
-        if (   ownerCount > MAX_OWNER_COUNT
-            || _required > ownerCount
-            || _required == 0
-            || ownerCount == 0)
-            throw;
+        require(ownerCount <= MAX_OWNER_COUNT
+            && _required <= ownerCount
+            && _required != 0
+            && ownerCount != 0);
         _;
     }
 
@@ -111,8 +102,7 @@ contract MultiSigWallet {
         validRequirement(_owners.length, _required)
     {
         for (uint i=0; i<_owners.length; i++) {
-            if (isOwner[_owners[i]] || _owners[i] == 0)
-                throw;
+            require(!isOwner[_owners[i]] && _owners[i] != 0);
             isOwner[_owners[i]] = true;
         }
         owners = _owners;
diff --git a/contracts/Haltable.sol b/contracts/Haltable.sol
index 63c2c001..8cb53fa3 100644
--- a/contracts/Haltable.sol
+++ b/contracts/Haltable.sol
@@ -21,17 +21,17 @@ contract Haltable is Ownable {
   bool public halted;
 
   modifier stopInEmergency {
-    if (halted) throw;
+    require(!halted);
     _;
   }
 
   modifier stopNonOwnersInEmergency {
-    if (halted && msg.sender != owner) throw;
+    require(!halted || msg.sender == owner);
     _;
   }
 
   modifier onlyInEmergency {
-    if (!halted) throw;
+    require(halted);
     _;
   }
 
diff --git a/contracts/Issuer.sol b/contracts/Issuer.sol
index 7962ae0e..95569a3d 100644
--- a/contracts/Issuer.sol
+++ b/contracts/Issuer.sol
@@ -43,7 +43,7 @@ contract Issuer is Ownable {
   }
 
   function issue(address benefactor, uint amount) onlyOwner {
-    if(issued[benefactor]) throw;
+    require(!issued[benefactor]);
     token.transferFrom(allower, benefactor, amount);
     issued[benefactor] = true;
     issuedCount += amount;
diff --git a/contracts/MilestonePricing.sol b/contracts/MilestonePricing.sol
index 3d8291a0..0a37fcc7 100644
--- a/contracts/MilestonePricing.sol
+++ b/contracts/MilestonePricing.sol
@@ -46,9 +46,7 @@ contract MilestonePricing is PricingStrategy, Ownable {
   /// @param _milestones uint[] milestones Pairs of (time, price)
   function MilestonePricing(uint[] _milestones) {
     // Need to have tuples, length check
-    if(_milestones.length % 2 == 1 || _milestones.length >= MAX_MILESTONE*2) {
-      throw;
-    }
+    require((_milestones.length % 2 == 0) && (_milestones.length <= MAX_MILESTONE*2));
 
     milestoneCount = _milestones.length / 2;
 
@@ -59,17 +57,13 @@ contract MilestonePricing is PricingStrategy, Ownable {
       milestones[i].price = _milestones[i*2+1];
 
       // No invalid steps
-      if((lastTimestamp != 0) && (milestones[i].time <= lastTimestamp)) {
-        throw;
-      }
+      require((lastTimestamp == 0) || (milestones[i].time > lastTimestamp));
 
       lastTimestamp = milestones[i].time;
     }
 
     // Last milestone price must be zero, terminating the crowdale
-    if(milestones[milestoneCount-1].price != 0) {
-      throw;
-    }
+    require(milestones[milestoneCount-1].price == 0);
   }
 
   /// @dev This is invoked once for every pre-ICO address, set pricePerToken
@@ -149,8 +143,8 @@ contract MilestonePricing is PricingStrategy, Ownable {
       return false;
   }
 
-  function() payable {
-    throw; // No money on this contract
+  function() {
+    // No money on this contract
   }
 
 }
diff --git a/contracts/MintableToken.sol b/contracts/MintableToken.sol
index d2e8d4e5..d3a57056 100644
--- a/contracts/MintableToken.sol
+++ b/contracts/MintableToken.sol
@@ -54,15 +54,13 @@ contract MintableToken is StandardTokenExt, Ownable {
 
   modifier onlyMintAgent() {
     // Only crowdsale contracts are allowed to mint new tokens
-    if(!mintAgents[msg.sender]) {
-        throw;
-    }
+    require(mintAgents[msg.sender]);
     _;
   }
 
   /** Make sure we are not done yet. */
   modifier canMint() {
-    if(mintingFinished) throw;
+    require(!mintingFinished);
     _;
   }
 }
diff --git a/contracts/PaymentForwarder.sol b/contracts/PaymentForwarder.sol
index 743869a3..2e0cbfe9 100644
--- a/contracts/PaymentForwarder.sol
+++ b/contracts/PaymentForwarder.sol
@@ -68,7 +68,7 @@ contract PaymentForwarder is Haltable {
     paymentsByBenefactor[benefactor] += weiAmount;
 
     // May run out of gas
-    if(!teamMultisig.send(weiAmount)) throw;
+    teamMultisig.transfer(weiAmount);
   }
 
   /**
diff --git a/contracts/PreICOProxyBuyer.sol b/contracts/PreICOProxyBuyer.sol
index 7004b412..e65f630e 100644
--- a/contracts/PreICOProxyBuyer.sol
+++ b/contracts/PreICOProxyBuyer.sol
@@ -87,21 +87,12 @@ contract PreICOProxyBuyer is Ownable, Haltable {
    */
   function PreICOProxyBuyer(address _owner, uint _freezeEndsAt, uint _weiMinimumLimit, uint _weiMaximumLimit, uint _weiCap) {
 
-    owner = _owner;
-
-    // Give argument
-    if(_freezeEndsAt == 0) {
-      throw;
-    }
-
     // Give argument
-    if(_weiMinimumLimit == 0) {
-      throw;
-    }
+    require(_freezeEndsAt != 0);
+    require(_weiMinimumLimit != 0);
+    require(_weiMaximumLimit != 0);
 
-    if(_weiMaximumLimit == 0) {
-      throw;
-    }
+    owner = _owner;
 
     weiMinimumLimit = _weiMinimumLimit;
     weiMaximumLimit = _weiMaximumLimit;
@@ -113,9 +104,7 @@ contract PreICOProxyBuyer is Ownable, Haltable {
    * Get the token we are distributing.
    */
   function getToken() public constant returns(FractionalERC20) {
-    if(address(crowdsale) == 0)  {
-      throw;
-    }
+    require(address(crowdsale) != 0);
 
     return crowdsale.token();
   }
@@ -126,9 +115,9 @@ contract PreICOProxyBuyer is Ownable, Haltable {
   function invest(uint128 customerId) private {
 
     // Cannot invest anymore through crowdsale when moving has begun
-    if(getState() != State.Funding) throw;
+    require(getState() == State.Funding);
 
-    if(msg.value == 0) throw; // No empty buys
+    require(msg.value != 0); // No empty buys
 
     address investor = msg.sender;
 
@@ -137,9 +126,7 @@ contract PreICOProxyBuyer is Ownable, Haltable {
     balances[investor] = balances[investor].add(msg.value);
 
     // Need to satisfy minimum and maximum limits
-    if(balances[investor] < weiMinimumLimit || balances[investor] > weiMaximumLimit) {
-      throw;
-    }
+    require(balances[investor] >= weiMinimumLimit && balances[investor] <= weiMaximumLimit);
 
     // This is a new investor
     if(!existing) {
@@ -148,9 +135,7 @@ contract PreICOProxyBuyer is Ownable, Haltable {
     }
 
     weiRaised = weiRaised.add(msg.value);
-    if(weiRaised > weiCap) {
-      throw;
-    }
+    require(weiRaised <= weiCap);
 
     // We will use the same event form the Crowdsale for compatibility reasons
     // despite not having a token amount.
@@ -173,13 +158,11 @@ contract PreICOProxyBuyer is Ownable, Haltable {
    */
   function buyForEverybody() stopNonOwnersInEmergency public {
 
-    if(getState() != State.Funding) {
-      // Only allow buy once
-      throw;
-    }
+    // Only allow buy once
+    require(getState() == State.Funding);
 
     // Crowdsale not yet set
-    if(address(crowdsale) == 0) throw;
+    require(address(crowdsale) != 0);
 
     // Buy tokens on the contract
     crowdsale.invest.value(weiRaised)(address(this));
@@ -187,10 +170,8 @@ contract PreICOProxyBuyer is Ownable, Haltable {
     // Record how many tokens we got
     tokensBought = getToken().balanceOf(address(this));
 
-    if(tokensBought == 0) {
-      // Did not get any tokens
-      throw;
-    }
+    // Did not get any tokens
+    require(tokensBought != 0);
 
     TokensBoughts(tokensBought);
   }
@@ -201,9 +182,7 @@ contract PreICOProxyBuyer is Ownable, Haltable {
   function getClaimAmount(address investor) public constant returns (uint) {
 
     // Claims can be only made if we manage to buy tokens
-    if(getState() != State.Distributing) {
-      throw;
-    }
+    require(getState() == State.Distributing);
     return balances[investor].mul(tokensBought) / weiRaised;
   }
 
@@ -228,14 +207,10 @@ contract PreICOProxyBuyer is Ownable, Haltable {
   function claim(uint amount) stopInEmergency {
     address investor = msg.sender;
 
-    if(amount == 0) {
-      throw;
-    }
+    require(amount != 0);
 
-    if(getClaimLeft(investor) < amount) {
-      // Woops we cannot get more than we have left
-      throw;
-    }
+    // Woops we cannot get more than we have left
+    require(getClaimLeft(investor) >= amount);
 
     // We track who many investor have (partially) claimed their tokens
     if(claimed[investor] == 0) {
@@ -255,13 +230,13 @@ contract PreICOProxyBuyer is Ownable, Haltable {
   function refund() stopInEmergency {
 
     // Trying to ask refund too soon
-    if(getState() != State.Refunding) throw;
+    require(getState() == State.Refunding);
 
     address investor = msg.sender;
-    if(balances[investor] == 0) throw;
+    require(balances[investor] != 0);
     uint amount = balances[investor];
     delete balances[investor];
-    if(!(investor.call.value(amount)())) throw;
+    investor.transfer(amount);
     Refunded(investor, amount);
   }
 
@@ -269,10 +244,10 @@ contract PreICOProxyBuyer is Ownable, Haltable {
    * Set the target crowdsale where we will move presale funds when the crowdsale opens.
    */
   function setCrowdsale(Crowdsale _crowdsale) public onlyOwner {
-    crowdsale = _crowdsale;
-
     // Check interface
-    if(!crowdsale.isCrowdsale()) true;
+    require(_crowdsale.isCrowdsale());
+
+    crowdsale = _crowdsale;
   }
 
   /// @dev This is used in the first case scenario, this will force the state
@@ -285,7 +260,7 @@ contract PreICOProxyBuyer is Ownable, Haltable {
   ///      we can't use Crowdsale's refund, since our default function does not
   ///      accept money in.
   function loadRefund() public payable {
-    if(getState() != State.Refunding) throw;
+    require(getState() == State.Refunding);
   }
 
   /**
@@ -312,7 +287,6 @@ contract PreICOProxyBuyer is Ownable, Haltable {
   }
 
   /** Explicitly call function from your wallet. */
-  function() payable {
-    throw;
+  function() {
   }
 }
diff --git a/contracts/PresaleFundCollector.sol b/contracts/PresaleFundCollector.sol
index 42ebd73c..e180e734 100644
--- a/contracts/PresaleFundCollector.sol
+++ b/contracts/PresaleFundCollector.sol
@@ -55,17 +55,11 @@ contract PresaleFundCollector is Ownable {
    */
   function PresaleFundCollector(address _owner, uint _freezeEndsAt, uint _weiMinimumLimit) {
 
-    owner = _owner;
-
     // Give argument
-    if(_freezeEndsAt == 0) {
-      throw;
-    }
+    require(_freezeEndsAt != 0);
+    require(_weiMinimumLimit != 0);
 
-    // Give argument
-    if(_weiMinimumLimit == 0) {
-      throw;
-    }
+    owner = _owner;
 
     weiMinimumLimit = _weiMinimumLimit;
     freezeEndsAt = _freezeEndsAt;
@@ -77,7 +71,7 @@ contract PresaleFundCollector is Ownable {
   function invest() public payable {
 
     // Cannot invest anymore through crowdsale when moving has begun
-    if(moving) throw;
+    require(!moving);
 
     address investor = msg.sender;
 
@@ -86,15 +80,13 @@ contract PresaleFundCollector is Ownable {
     balances[investor] = balances[investor].plus(msg.value);
 
     // Need to fulfill minimum limit
-    if(balances[investor] < weiMinimumLimit) {
-      throw;
-    }
+    require(balances[investor] >= weiMinimumLimit);
 
     // This is a new investor
     if(!existing) {
 
       // Limit number of investors to prevent too long loops
-      if(investorCount >= MAX_INVESTORS) throw;
+      require(investorCount < MAX_INVESTORS);
 
       investors.push(investor);
       investorCount++;
@@ -109,7 +101,7 @@ contract PresaleFundCollector is Ownable {
   function participateCrowdsaleInvestor(address investor) public {
 
     // Crowdsale not yet set
-    if(address(crowdsale) == 0) throw;
+    require(address(crowdsale) != 0);
 
     moving = true;
 
@@ -139,16 +131,16 @@ contract PresaleFundCollector is Ownable {
   function refund() {
 
     // Trying to ask refund too soon
-    if(now < freezeEndsAt) throw;
+    require(now >= freezeEndsAt);
 
     // We have started to move funds
     moving = true;
 
     address investor = msg.sender;
-    if(balances[investor] == 0) throw;
+    require(balances[investor] != 0);
     uint amount = balances[investor];
     delete balances[investor];
-    if(!investor.send(amount)) throw;
+    investor.transfer(amount);
     Refunded(investor, amount);
   }
 
@@ -160,7 +152,6 @@ contract PresaleFundCollector is Ownable {
   }
 
   /** Explicitly call function from your wallet. */
-  function() payable {
-    throw;
+  function() {
   }
 }
diff --git a/contracts/RelaunchedCrowdsale.sol b/contracts/RelaunchedCrowdsale.sol
index 22703a03..c52cc21d 100644
--- a/contracts/RelaunchedCrowdsale.sol
+++ b/contracts/RelaunchedCrowdsale.sol
@@ -59,16 +59,12 @@ contract RelaunchedCrowdsale is MintedTokenCappedCrowdsale {
   function setInvestorDataAndIssueNewToken(address _addr, uint _weiAmount, uint _tokenAmount, uint _originalTxHash) onlyOwner public {
 
     // This transaction has already been rebuild
-    if(reissuedTransactions[_originalTxHash]) {
-      throw;
-    }
+    require(!reissuedTransactions[_originalTxHash]);
 
     setInvestorData(_addr, _weiAmount, _tokenAmount, _originalTxHash);
 
     // Check that we did not bust the cap in the restoration process
-    if(isBreakingCap(_weiAmount, _tokenAmount, weiRaised, tokensSold)) {
-      throw;
-    }
+    require(!isBreakingCap(_weiAmount, _tokenAmount, weiRaised, tokensSold));
 
     // Mark transaction processed
     reissuedTransactions[_originalTxHash] = true;
diff --git a/contracts/ReleasableToken.sol b/contracts/ReleasableToken.sol
index 18dfd302..b09b5624 100644
--- a/contracts/ReleasableToken.sol
+++ b/contracts/ReleasableToken.sol
@@ -29,13 +29,7 @@ contract ReleasableToken is ERC20, Ownable {
    *
    */
   modifier canTransfer(address _sender) {
-
-    if(!released) {
-        if(!transferAgents[_sender]) {
-            throw;
-        }
-    }
-
+    require(released || transferAgents[_sender]);
     _;
   }
 
@@ -68,17 +62,13 @@ contract ReleasableToken is ERC20, Ownable {
 
   /** The function can be called only before or after the tokens have been releasesd */
   modifier inReleaseState(bool releaseState) {
-    if(releaseState != released) {
-        throw;
-    }
+    require(releaseState == released);
     _;
   }
 
   /** The function can be called only by a whitelisted release agent. */
   modifier onlyReleaseAgent() {
-    if(msg.sender != releaseAgent) {
-        throw;
-    }
+    require(msg.sender == releaseAgent);
     _;
   }
 
diff --git a/contracts/TimeVault.sol b/contracts/TimeVault.sol
index aa29b8ee..ea50b8cf 100644
--- a/contracts/TimeVault.sol
+++ b/contracts/TimeVault.sol
@@ -34,14 +34,13 @@ contract TimeVault {
   event Unlocked();
 
   function TimeVault(address _teamMultisig, StandardTokenExt _token, uint _unlockedAt) {
+    // Sanity check
+    require(_teamMultisig != 0x0);
+    require(address(_token) != 0x0);
 
     teamMultisig = _teamMultisig;
     token = _token;
     unlockedAt = _unlockedAt;
-
-    // Sanity check
-    if (teamMultisig == 0x0) throw;
-    if (address(token) == 0x0) throw;
   }
 
   function getTokenBalance() public constant returns (uint) {
@@ -50,7 +49,7 @@ contract TimeVault {
 
   function unlock() public {
     // Wait your turn!
-    if (now < unlockedAt) throw;
+    require(now >= unlockedAt);
 
     // StandardToken will throw in the case of transaction fails
     token.transfer(teamMultisig, getTokenBalance());
@@ -59,6 +58,7 @@ contract TimeVault {
   }
 
   // disallow ETH payment for this vault
-  function () { throw; }
+  function () {
+  }
 
 }
diff --git a/contracts/TokenTranchePricing.sol b/contracts/TokenTranchePricing.sol
index a6464b5f..9b545029 100644
--- a/contracts/TokenTranchePricing.sol
+++ b/contracts/TokenTranchePricing.sol
@@ -48,9 +48,7 @@ contract TokenTranchePricing is PricingStrategy, Ownable {
   /// @param _tranches uint[] tranches Pairs of (start amount, price)
   function TokenTranchePricing(uint[] _tranches) {
     // Need to have tuples, length check
-    if(_tranches.length % 2 == 1 || _tranches.length >= MAX_TRANCHES*2) {
-      throw;
-    }
+    require((_tranches.length % 2 == 0) && (_tranches.length <= MAX_TRANCHES*2));
 
     trancheCount = _tranches.length / 2;
 
@@ -61,17 +59,13 @@ contract TokenTranchePricing is PricingStrategy, Ownable {
       tranches[i].price = _tranches[i*2+1];
 
       // No invalid steps
-      if((highestAmount != 0) && (tranches[i].amount <= highestAmount)) {
-        throw;
-      }
+      require((highestAmount == 0) || (tranches[i].amount > highestAmount));
 
       highestAmount = tranches[i].amount;
     }
 
     // Last tranche price must be zero, terminating the crowdale
-    if(tranches[trancheCount-1].price != 0) {
-      throw;
-    }
+    require(tranches[trancheCount-1].price == 0);
   }
 
   /// @dev This is invoked once for every pre-ICO address, set pricePerToken
@@ -149,8 +143,8 @@ contract TokenTranchePricing is PricingStrategy, Ownable {
     return value.times(multiplier) / price;
   }
 
-  function() payable {
-    throw; // No money on this contract
+  function() {
+    // No money on this contract
   }
 
 }
diff --git a/contracts/TokenVault.sol b/contracts/TokenVault.sol
index 455eb068..337e96ad 100644
--- a/contracts/TokenVault.sol
+++ b/contracts/TokenVault.sol
@@ -81,29 +81,22 @@ contract TokenVault is Ownable {
    */
   function TokenVault(address _owner, uint _freezeEndsAt, CrowdsaleToken _token, uint _tokensToBeAllocated) {
 
-    owner = _owner;
 
     // Invalid owenr
-    if(owner == 0) {
-      throw;
-    }
-
-    token = _token;
+    require(_owner != 0);
 
     // Check the address looks like a token contract
-    if(!token.isToken()) {
-      throw;
-    }
+    require(_token.isToken());
 
     // Give argument
-    if(_freezeEndsAt == 0) {
-      throw;
-    }
+    require(_freezeEndsAt != 0);
 
     // Sanity check on _tokensToBeAllocated
-    if(_tokensToBeAllocated == 0) {
-      throw;
-    }
+    require(_tokensToBeAllocated != 0);
+
+    owner = _owner;
+
+    token = _token;
 
     freezeEndsAt = _freezeEndsAt;
     tokensToBeAllocated = _tokensToBeAllocated;
@@ -112,17 +105,13 @@ contract TokenVault is Ownable {
   /// @dev Add a presale participating allocation
   function setInvestor(address investor, uint amount) public onlyOwner {
 
-    if(lockedAt > 0) {
-      // Cannot add new investors after the vault is locked
-      throw;
-    }
+    // Cannot add new investors after the vault is locked
+    require(lockedAt == 0);
 
-    if(amount == 0) throw; // No empty buys
+    require(amount != 0); // No empty buys
 
     // Don't allow reset
-    if(balances[investor] > 0) {
-      throw;
-    }
+    require(balances[investor] == 0);
 
     balances[investor] = amount;
 
@@ -139,19 +128,13 @@ contract TokenVault is Ownable {
   ///      - Checks are in place to prevent creating a vault that is locked with incorrect token balances.
   function lock() onlyOwner {
 
-    if(lockedAt > 0) {
-      throw; // Already locked
-    }
+    require(lockedAt == 0); // Already locked
 
     // Spreadsheet sum does not match to what we have loaded to the investor data
-    if(tokensAllocatedTotal != tokensToBeAllocated) {
-      throw;
-    }
+    require(tokensAllocatedTotal == tokensToBeAllocated);
 
     // Do not lock the vault if the given tokens are not on this contract
-    if(token.balanceOf(address(this)) != tokensAllocatedTotal) {
-      throw;
-    }
+    require(token.balanceOf(address(this)) == tokensAllocatedTotal);
 
     lockedAt = now;
 
@@ -160,9 +143,7 @@ contract TokenVault is Ownable {
 
   /// @dev In the case locking failed, then allow the owner to reclaim the tokens on the contract.
   function recoverFailedLock() onlyOwner {
-    if(lockedAt > 0) {
-      throw;
-    }
+    require(lockedAt == 0);
 
     // Transfer all tokens on this contract back to the owner
     token.transfer(owner, token.balanceOf(address(this)));
@@ -179,22 +160,13 @@ contract TokenVault is Ownable {
 
     address investor = msg.sender;
 
-    if(lockedAt == 0) {
-      throw; // We were never locked
-    }
+    require(lockedAt > 0); // We were never locked
 
-    if(now < freezeEndsAt) {
-      throw; // Trying to claim early
-    }
+    require(now >= freezeEndsAt); // Trying to claim early
 
-    if(balances[investor] == 0) {
-      // Not our investor
-      throw;
-    }
+    require(balances[investor] != 0); // Not our investor
 
-    if(claimed[investor] > 0) {
-      throw; // Already claimed
-    }
+    require(claimed[investor] == 0); // Already claimed
 
     uint amount = balances[investor];
 
diff --git a/contracts/UpgradeableToken.sol b/contracts/UpgradeableToken.sol
index fe12033a..8033299c 100644
--- a/contracts/UpgradeableToken.sol
+++ b/contracts/UpgradeableToken.sol
@@ -60,13 +60,10 @@ contract UpgradeableToken is StandardTokenExt {
   function upgrade(uint256 value) public {
 
       UpgradeState state = getUpgradeState();
-      if(!(state == UpgradeState.ReadyToUpgrade || state == UpgradeState.Upgrading)) {
-        // Called in a bad state
-        throw;
-      }
+      require(state == UpgradeState.ReadyToUpgrade || state == UpgradeState.Upgrading); // Called in a bad state
 
       // Validate input value.
-      if (value == 0) throw;
+      require(value != 0);
 
       balances[msg.sender] = balances[msg.sender].sub(value);
 
@@ -84,23 +81,21 @@ contract UpgradeableToken is StandardTokenExt {
    */
   function setUpgradeAgent(address agent) external {
 
-      if(!canUpgrade()) {
-        // The token is not yet in a state that we could think upgrading
-        throw;
-      }
+      // The token is not yet in a state that we could think upgrading
+      require(canUpgrade());
 
-      if (agent == 0x0) throw;
+      require(agent != 0x0);
       // Only a master can designate the next agent
-      if (msg.sender != upgradeMaster) throw;
+      require(msg.sender == upgradeMaster);
       // Upgrade has already begun for an agent
-      if (getUpgradeState() == UpgradeState.Upgrading) throw;
+      require(getUpgradeState() != UpgradeState.Upgrading);
 
       upgradeAgent = UpgradeAgent(agent);
 
       // Bad interface
-      if(!upgradeAgent.isUpgradeAgent()) throw;
+      require(upgradeAgent.isUpgradeAgent());
       // Make sure that token supplies match in source and target
-      if (upgradeAgent.originalSupply() != totalSupply) throw;
+      require(upgradeAgent.originalSupply() == totalSupply);
 
       UpgradeAgentSet(upgradeAgent);
   }
@@ -121,8 +116,8 @@ contract UpgradeableToken is StandardTokenExt {
    * This allows us to set a new owner for the upgrade mechanism.
    */
   function setUpgradeMaster(address master) public {
-      if (master == 0x0) throw;
-      if (msg.sender != upgradeMaster) throw;
+      require(master != 0x0);
+      require(msg.sender == upgradeMaster);
       upgradeMaster = master;
   }
 
diff --git a/contracts/test/TestMigrationTarget.sol b/contracts/test/TestMigrationTarget.sol
index 82ee0f41..74564ea2 100644
--- a/contracts/test/TestMigrationTarget.sol
+++ b/contracts/test/TestMigrationTarget.sol
@@ -22,19 +22,15 @@ contract TestMigrationTarget is StandardTokenExt, UpgradeAgent {
     oldToken = _oldToken;
 
     // Let's not set bad old token
-    if(address(oldToken) == 0) {
-      throw;
-    }
+    require(address(oldToken) != 0);
 
     // Let's make sure we have something to migrate
     originalSupply = _oldToken.totalSupply();
-    if(originalSupply == 0) {
-      throw;
-    }
+    require(originalSupply != 0);
   }
 
   function upgradeFrom(address _from, uint256 _value) public {
-    if (msg.sender != address(oldToken)) throw; // only upgrade from oldToken
+    require(msg.sender == address(oldToken)); // only upgrade from oldToken
 
     // Mint new tokens to the migrator
     totalSupply = totalSupply.plus(_value);
@@ -42,8 +38,7 @@ contract TestMigrationTarget is StandardTokenExt, UpgradeAgent {
     Transfer(0, _from, _value);
   }
 
-  function() public payable {
-    throw;
+  function() public {
   }
 
 }
diff --git a/zeppelin b/zeppelin
index 287b873a..1df75a95 160000
--- a/zeppelin
+++ b/zeppelin
@@ -1 +1 @@
-Subproject commit 287b873add003494828c143f74f631224aa219f4
+Subproject commit 1df75a951f37a176303df5cc60b689001948d7cc