diff --git a/src/proto/if_python3.pro b/src/proto/if_python3.pro
index d2bcd8c..0e139b9 100644
--- a/src/proto/if_python3.pro
+++ b/src/proto/if_python3.pro
@@ -10,5 +10,5 @@
 void python3_tabpage_free(tabpage_T *tab);
 void do_py3eval(char_u *str, typval_T *rettv);
 int set_ref_in_python3(int copyID);
-int python3_version();
+int python3_version(void);
 /* vim: set ft=c : */