diff --git a/p4_hlir/frontend/semantic_check.py b/p4_hlir/frontend/semantic_check.py
index 8beca16..cc7181d 100644
--- a/p4_hlir/frontend/semantic_check.py
+++ b/p4_hlir/frontend/semantic_check.py
@@ -1731,7 +1731,7 @@ def check_P4Register(self, symbols, header_fields, objects, types = None):
 
     if self.layout:
         p4_type = self.layout.check_ts(symbols, header_fields, objects)
-        if p4_type is not None and p4_type.type_ == Types.header_type:
+        if p4_type is None or p4_type.type_ != Types.header_type:
             error_msg = "Error in register %s defined in file %s at line %d:"\
                         " layout attribute needs to refer to header type"\
                         % (self.name, self.filename, self.lineno)
diff --git a/tests/control_flow_opt.p4 b/tests/control_flow_opt.p4
index 7b33f61..9df5f6e 100644
--- a/tests/control_flow_opt.p4
+++ b/tests/control_flow_opt.p4
@@ -1,12 +1,12 @@
 #include "includes/headers.p4"
 #include "includes/parser.p4"
 
-action hop(ttl, egress_spec) {
-    add_to_field(ttl, -1);
+action hop(bit<8> ttl, bit<8> egress_spec) {
+    modify_field(ttl, ttl - 1);
     modify_field(standard_metadata.egress_spec, egress_spec, 0xFFFFFFFF);
 }
 
-action hop_ipv4(egress_spec) {
+action hop_ipv4(bit<8> egress_spec) {
     hop(ipv4.ttl, egress_spec);
 }
 
@@ -85,4 +85,4 @@ control ingress {
 
 control egress {
 
-}
\ No newline at end of file
+}
diff --git a/tests/includes/headers.p4 b/tests/includes/headers.p4
index a808539..438084f 100644
--- a/tests/includes/headers.p4
+++ b/tests/includes/headers.p4
@@ -1,93 +1,93 @@
 header_type ethernet_t {
     fields {
-        dstAddr : 48;
-        srcAddr : 48;
-        etherType : 16;
+        bit<48> dstAddr;
+        bit<48> srcAddr;
+        bit<16> etherType;
     }
 }
 
 header_type vlan_tag_t {
     fields {
-        pcp : 3;
-        cfi : 1;
-        vid : 12;
-        etherType : 16;
+        bit<3> pcp;
+        bit<1> cfi;
+        bit<12> vid;
+        bit<16> etherType;
     }
 }
 
 header_type ipv4_t {
     fields {
-        version : 4;
-        ihl : 4;
-        diffserv : 8;
-        totalLen : 16;
-        identification : 16;
-        flags : 3;
-        fragOffset : 13;
-        ttl : 8;
-        protocol : 8;
-        hdrChecksum : 16;
-        srcAddr : 32;
-        dstAddr: 32;
+        bit<4> version;
+        bit<4> ihl;
+        bit<8> diffserv;
+        bit<16> totalLen;
+        bit<16> identification;
+        bit<3> flags;
+        bit<13> fragOffset;
+        bit<8> ttl;
+        bit<8> protocol;
+        bit<16> hdrChecksum;
+        bit<32> srcAddr;
+        bit<32> dstAddr;
     }
 }
 
 header_type ipv6_t {
     fields {
-        version : 4;
-        trafficClass : 8;
-        flowLabel : 20;
-        payloadLen : 16;
-        nextHdr : 8;
-        hopLimit : 8;
-        srcAddr : 128;
-        dstAddr : 128;
+        bit<4> version;
+        bit<8> trafficClass;
+        bit<20> flowLabel;
+        bit<16> payloadLen;
+        bit<8> nextHdr;
+        bit<8> hopLimit;
+        bit<128> srcAddr;
+        bit<128> dstAddr;
     }
 }
 
 header_type icmp_t {
     fields {
-        hdr_type : 8;
-        code : 8;
-        hdrChecksum : 16;
+        bit<8> hdr_type;
+        bit<8> code;
+        bit<16> hdrChecksum;
     }
 }
 
 header_type icmpv6_t {
     fields {
-        hdr_type : 8;
-        code : 8;
-        hdrChecksum : 16;
+        bit<8> hdr_type;
+        bit<8> code;
+        bit<16> hdrChecksum;
     }
 }
 
 header_type tcp_t {
     fields {
-        srcPort : 16;
-        dstPort : 16;
-        seqNo : 32;
-        ackNo : 32;
-        dataOffset : 4;
-        res : 3;
-        ecn : 3;
-        ctrl : 6;
-        window : 16;
-        checksum : 16;
-        urgentPtr : 16;
+        bit<16> srcPort;
+        bit<16> dstPort;
+        bit<32> seqNo;
+        bit<32> ackNo;
+        bit<4> dataOffset;
+        bit<3> res;
+        bit<3> ecn;
+        bit<6> ctrl;
+        bit<16> window;
+        bit<16> checksum;
+        bit<16> urgentPtr;
     }
 }
 
 header_type udp_t {
     fields {
-        srcPort : 16;
-        dstPort : 16;
-        hdr_length : 16;
-        checksum : 16;
+        bit<16> srcPort;
+        bit<16> dstPort;
+        bit<16> hdr_length;
+        bit<16> checksum;
     }
 }
 
 header_type routing_metadata_t {
     fields {
-        drop : 1;
+        bit<1> drop;
     }
-}
\ No newline at end of file
+}
diff --git a/tests/stateful.p4 b/tests/stateful.p4
index 71455c1..fcba6d6 100644
--- a/tests/stateful.p4
+++ b/tests/stateful.p4
@@ -1,12 +1,12 @@
 #include "includes/headers.p4"
 #include "includes/parser.p4"
 
-action hop(ttl, egress_spec) {
-    add_to_field(ttl, -1);
-    modify_field(standard_metadata.egress_spec, egress_spec, 0xFFFFFFFF);
+action hop(bit<8> ttl, bit<8> egress_spec) {
+    	modify_field(ttl, ttl - 1);
+	modify_field(standard_metadata.egress_spec, egress_spec, 0xFFFFFFFF);
 }
 
-action hop_ipv4(egress_spec) {
+action hop_ipv4(bit<8> egress_spec) {
     hop(ipv4.ttl, egress_spec);
 }
 
@@ -50,7 +50,7 @@ register reg1 {
     instance_count : 100;
     attributes : saturating, signed;
 }
-
+ 
 register reg2 {
     layout : ipv4_t;
     direct : ipv4_routing;
@@ -64,4 +64,4 @@ control ingress {
 
 control egress {
 
-}
\ No newline at end of file
+}