diff --git a/src/proto/term.pro b/src/proto/term.pro
index 9958763..720d028 100644
--- a/src/proto/term.pro
+++ b/src/proto/term.pro
@@ -34,6 +34,7 @@
 void starttermcap __ARGS((void));
 void stoptermcap __ARGS((void));
 void may_req_termresponse __ARGS((void));
+void may_req_ambiguous_character_width __ARGS((void));
 int swapping_screen __ARGS((void));
 void setmouse __ARGS((void));
 int mouse_has __ARGS((int c));