diff --git a/p4src/actions_delta_checksum.p4 b/p4src/actions_delta_checksum.p4
index 958dc18..42291ff 100644
--- a/p4src/actions_delta_checksum.p4
+++ b/p4src/actions_delta_checksum.p4
@@ -48,7 +48,7 @@ action v6sum() {
     tmp = tmp + (bit<32>) hdr.ipv6.next_header;                 // 8 bit
 
     carryover = tmp >> 16;            /* maximum is 18*(2**16)  >> 16 == 18 */
-ffff) + carryover; /* Now tmp contains at maximum 65554*/
+    tmp = (tmp & 0xffff) + carryover; /* Now tmp contains at maximum 65554*/
     carryover = tmp >> 16;            /* Now carryover contains at maximum 1 */
     tmp = tmp + carryover;            /* No overrun possible anymore */