diff --git a/src/proto/if_lua.pro b/src/proto/if_lua.pro
index 8db66a6..10395d5 100644
--- a/src/proto/if_lua.pro
+++ b/src/proto/if_lua.pro
@@ -7,5 +7,5 @@
 void lua_buffer_free __ARGS((buf_T *buf));
 void lua_window_free __ARGS((win_T *win));
 void do_luaeval __ARGS((char_u *str, typval_T *arg, typval_T *rettv));
-void set_ref_in_lua __ARGS((int copyID));
+int set_ref_in_lua __ARGS((int copyID));
 /* vim: set ft=c : */