diff --git a/libavformat/udp.c b/libavformat/udp.c
index b6a4724309..affa08ea00 100644
--- a/libavformat/udp.c
+++ b/libavformat/udp.c
@@ -591,7 +591,7 @@ static int udp_open(URLContext *h, const char *uri, int flags)
             goto fail;
     }
 
-    if (s->pkt_size)
+    if (s->pkt_size > 0)
         h->max_packet_size = s->pkt_size;
 
     p = strchr(uri, '?');