diff --git a/src/proto/vim9script.pro b/src/proto/vim9script.pro
index cb5a30d..2c4bd79 100644
--- a/src/proto/vim9script.pro
+++ b/src/proto/vim9script.pro
@@ -5,6 +5,7 @@
 int not_in_vim9(exarg_T *eap);
 int vim9_bad_comment(char_u *p);
 int vim9_comment_start(char_u *p);
+void ex_incdec(exarg_T *eap);
 void ex_export(exarg_T *eap);
 void free_imports_and_script_vars(int sid);
 void mark_imports_for_reload(int sid);