diff --git a/src/proto/if_python3.pro b/src/proto/if_python3.pro
index 1e2a522..8d0489c 100644
--- a/src/proto/if_python3.pro
+++ b/src/proto/if_python3.pro
@@ -9,5 +9,5 @@
 void python3_window_free __ARGS((win_T *win));
 void python3_tabpage_free __ARGS((tabpage_T *tab));
 void do_py3eval __ARGS((char_u *str, typval_T *rettv));
-void set_ref_in_python3 __ARGS((int copyID));
+int set_ref_in_python3 __ARGS((int copyID));
 /* vim: set ft=c : */