diff --git a/src/Spectre.sol b/src/Spectre.sol
index e6cb7d0..bd40126 100644
--- a/src/Spectre.sol
+++ b/src/Spectre.sol
@@ -16,6 +16,8 @@ contract Spectre {
 
     uint256 internal immutable SLOTS_PER_PERIOD;
 
+    uint256 internal constant MIN_SYNC_COMMITTEE_PARTICIPANTS = 10;
+
     /// Maps from a sync period to the poseidon commitment for the sync committee.
     mapping(uint256 => uint256) public syncCommitteePoseidons;
 
@@ -60,6 +62,11 @@ contract Spectre {
             "Sync committee not yet set for this period"
         );
 
+        require(
+            input.participation > MIN_SYNC_COMMITTEE_PARTICIPANTS,
+            "Less than MIN_SYNC_COMMITTEE_PARTICIPANTS signed"
+        );
+
         _verifyStepProof(input, proof, syncCommitteePoseidons[currentPeriod]);
 
         // update the contract state