diff --git a/src/hlua.c b/src/hlua.c
index a52a1b5..8ad9e9f 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -8640,6 +8640,9 @@
 	struct hlua_mem_allocator *zone = ud;
 	size_t limit, old, new;
 
+	if (unlikely(!ptr && !nsize))
+		return NULL;
+
 	/* a limit of ~0 means unlimited and boot complete, so there's no need
 	 * for accounting anymore.
 	 */