diff --git a/input/ar.c b/input/ar.c
index 0827b8be83..a71f3d3eb4 100644
--- a/input/ar.c
+++ b/input/ar.c
@@ -303,7 +303,7 @@ mp_input_ar_init_error:
     return -1;
 }
 
-int is_mplayer_front(void)
+static int is_mplayer_front(void)
 {
     ProcessSerialNumber myProc, frProc;
     Boolean sameProc;