diff --git a/src/proto/os_macosx.pro b/src/proto/os_macosx.pro
index 5b96b75..c7f94ec 100644
--- a/src/proto/os_macosx.pro
+++ b/src/proto/os_macosx.pro
@@ -1,7 +1,7 @@
 /* os_macosx.m */
-void process_cfrunloop();
+void process_cfrunloop(void);
 bool sound_mch_play(const char_u* event, long sound_id, soundcb_T *callback, bool playfile);
 void sound_mch_stop(long sound_id);
-void sound_mch_clear();
-void sound_mch_free();
+void sound_mch_clear(void);
+void sound_mch_free(void);
 /* vim: set ft=c : */