diff --git a/core.c b/core.c
index 8a1796f..6131a3c 100644
--- a/core.c
+++ b/core.c
@@ -121,7 +121,7 @@
 {
 	void *buf;
 
-	assert(size < (pkt->size - pkt->end));
+	assert(size <= (pkt->size - pkt->end));
 	buf = pkt->data + pkt->end;
 	pkt->end += size;
 	return buf;