diff --git a/utils/gtp_echo_responder.c b/utils/gtp_echo_responder.c
index e077c81..390fa25 100644
--- a/utils/gtp_echo_responder.c
+++ b/utils/gtp_echo_responder.c
@@ -125,7 +125,7 @@
 
 	res = strtoul(arg, &end, 0);
 	if ((errno == ERANGE && res == ULONG_MAX) || (errno && !res) ||
-	    arg == end) {
+	    arg == end || *end != '\0') {
 		fprintf(stderr, "Failed parsing Node Features bitmask: '%s'\n", arg);
 		exit(1);
 	}