diff --git a/editors/diff.c b/editors/diff.c
index 1359af8..f9e82ba 100644
--- a/editors/diff.c
+++ b/editors/diff.c
@@ -1205,7 +1205,7 @@
 
 
 int diff_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-int diff_main(int argc, char **argv)
+int diff_main(int argc ATTRIBUTE_UNUSED, char **argv)
 {
 	bool gotstdin = 0;
 	char *U_opt;