--- src/raptor_parse.c
+++ src/raptor_parse.c
@@ -257,7 +257,7 @@
 int
 raptor_world_get_parsers_count(raptor_world* world)
 {
-  RAPTOR_ASSERT_OBJECT_POINTER_RETURN_VALUE(world, raptor_world, NULL);
+  RAPTOR_ASSERT_OBJECT_POINTER_RETURN_VALUE(world, raptor_world, 0);
 
   raptor_world_open(world);
 
--- src/raptor_serialize.c
+++ src/raptor_serialize.c
@@ -240,7 +240,7 @@
 int
 raptor_world_get_serializers_count(raptor_world* world)
 {
-  RAPTOR_ASSERT_OBJECT_POINTER_RETURN_VALUE(world, raptor_world, NULL);
+  RAPTOR_ASSERT_OBJECT_POINTER_RETURN_VALUE(world, raptor_world, 0);
 
   raptor_world_open(world);