diff --git a/Include/mappingobject.h b/Include/mappingobject.h
index f6d36e0..7d006dd 100644
--- a/Include/mappingobject.h
+++ b/Include/mappingobject.h
@@ -44,6 +44,7 @@
 extern object *getmappingkeys PROTO((object *mp));
 extern object *getmappingvalues PROTO((object *mp));
 extern object *getmappingitems PROTO((object *mp));
+extern int getmappingsize PROTO((object *mp));
 
 #ifdef __cplusplus
 }