diff --git a/test/unit/slab_arena.c b/test/unit/slab_arena.c
index 9533377e497ff445cb5f04676274c17d6713a23d..e0c27cb1c8dd1e6a7b0b1c34b083b92e325e9ddd 100644
--- a/test/unit/slab_arena.c
+++ b/test/unit/slab_arena.c
@@ -25,7 +25,7 @@ int main()
 	void *ptr = slab_map(&arena);
 	slab_arena_print(&arena);
 	void *ptr1 = slab_map(&arena);
-	printf("going beyond the limit: %p\n", ptr1);
+	printf("going beyond the limit: %s\n", ptr1 ? "(ptr)" : "(nil)");
 	slab_arena_print(&arena);
 	slab_unmap(&arena, ptr);
 	slab_unmap(&arena, ptr1);