diff --git a/src/proto/diff.pro b/src/proto/diff.pro
index 9c34dcf..5141e37 100644
--- a/src/proto/diff.pro
+++ b/src/proto/diff.pro
@@ -14,6 +14,7 @@
 void ex_diffoff(exarg_T *eap);
 void diff_clear(tabpage_T *tp);
 int diff_check(win_T *wp, linenr_T lnum);
+int diff_check_with_linestatus(win_T *wp, linenr_T lnum, int *linestatus);
 int diff_check_fill(win_T *wp, linenr_T lnum);
 void diff_set_topline(win_T *fromwin, win_T *towin);
 int diffopt_changed(void);