diff --git a/Include/frameobject.h b/Include/frameobject.h
index e1f8190..dd36468 100644
--- a/Include/frameobject.h
+++ b/Include/frameobject.h
@@ -81,3 +81,7 @@
 
 void setup_block PROTO((frameobject *, int, int, int));
 block *pop_block PROTO((frameobject *));
+
+/* Extend the value stack */
+
+object **extend_stack PROTO((frameobject *, int, int));