diff --git a/src/event/ngx_event_udp.c b/src/event/ngx_event_udp.c
index d0c766062..d6b11d0b6 100644
--- a/src/event/ngx_event_udp.c
+++ b/src/event/ngx_event_udp.c
@@ -279,6 +279,8 @@ ngx_event_recvmsg(ngx_event_t *ev)
 
             buf.pos = buffer;
             buf.last = buffer + n;
+            buf.start = buf.pos;
+            buf.end = buffer + sizeof(buffer);
 
             rev = c->read;