diff --git a/dtool/src/parser-inc/stdtypedefs.h b/dtool/src/parser-inc/stdtypedefs.h
index c1febd3955..f971d7e1f2 100644
--- a/dtool/src/parser-inc/stdtypedefs.h
+++ b/dtool/src/parser-inc/stdtypedefs.h
@@ -41,6 +41,11 @@ inline namespace std {
 
 struct timeval;
 
+#ifdef __cplusplus
+#define NULL 0L
+#else
+#define NULL ((void *)0)
+#endif
 typedef decltype(nullptr) nullptr_t;
 
 // One day, we might extend interrogate to be able to parse this,