diff --git a/diff.h b/diff.h
index ce5e8a8..3197a97 100644
--- a/diff.h
+++ b/diff.h
@@ -436,7 +436,8 @@ int diff_result_code(struct diff_options *, int);
 
 void diff_no_index(struct repository *, struct rev_info *, int, const char **);
 
-int index_differs_from(const char *def, const struct diff_flags *flags,
+int index_differs_from(struct repository *r, const char *def,
+		       const struct diff_flags *flags,
 		       int ita_invisible_in_index);
 
 /*