--- a/src/checksums.c
+++ b/src/checksums.c
@@ -172,7 +172,7 @@ uint32_t udpchecksum(const void *l3pdu,
     int i;
 
     const struct udphdr *udp_hdr = (const struct udphdr *)l4pdu;
-    if (!udp_hdr->check) {
+    if (!udp_hdr->uh_sum) {
 	if (v6)
 	    // v6 requires checksums
 	    return -1;