diff --git a/src/proto/undo.pro b/src/proto/undo.pro
index 5114ed079a17fb2e4b9b007c3580e4d8aef34ba3..62dededdd9b7ae2fb18e93428f61335377d61529 100644
--- a/src/proto/undo.pro
+++ b/src/proto/undo.pro
@@ -6,6 +6,7 @@ int u_inssub __ARGS((linenr_T lnum));
 int u_savedel __ARGS((linenr_T lnum, long nlines));
 void u_undo __ARGS((int count));
 void u_redo __ARGS((int count));
+void undo_time __ARGS((int step));
 void u_sync __ARGS((void));
 void ex_undojoin __ARGS((exarg_T *eap));
 void u_unchanged __ARGS((buf_T *buf));