diff --git a/src/timesync/timesyncd-manager.c b/src/timesync/timesyncd-manager.c
index 8bd111fe0c..a6d336c461 100644
--- a/src/timesync/timesyncd-manager.c
+++ b/src/timesync/timesyncd-manager.c
@@ -552,7 +552,7 @@ static int manager_receive_response(sd_event_source *source, int fd, uint32_t re
 
         /* check our "time cookie" (we just stored nanoseconds in the fraction field) */
         if (be32toh(ntpmsg.origin_time.sec) != m->trans_time.tv_sec + OFFSET_1900_1970 ||
-            be32toh(ntpmsg.origin_time.frac) != m->trans_time.tv_nsec) {
+            be32toh(ntpmsg.origin_time.frac) != (unsigned long) m->trans_time.tv_nsec) {
                 log_debug("Invalid reply; not our transmit time. Ignoring.");
                 return 0;
         }