diff --git a/p4src/wraptest.p4 b/p4src/wraptest.p4
index 5c7a0f9..139bb32 100644
--- a/p4src/wraptest.p4
+++ b/p4src/wraptest.p4
@@ -25,7 +25,7 @@ control MyIngress(inout headers hdr,
         if(hdr.tcp.isValid()) {
             /* test wrap around */
             hdr.tcp.checksum = 0xffff;
-            hdr.tcp.checksum = checksum + 2;
+            hdr.tcp.checksum = hdr.tcp.checksum + 2;
         }
         standard_metadata.egress_spec = 1;
     }