diff --git a/libs/backends/coreaudio/coreaudio_backend.cc b/libs/backends/coreaudio/coreaudio_backend.cc
index 50477b6d08..8efcd0f32e 100644
--- a/libs/backends/coreaudio/coreaudio_backend.cc
+++ b/libs/backends/coreaudio/coreaudio_backend.cc
@@ -1247,7 +1247,7 @@ CoreAudioBackend::get_midi_event_count (void* port_buffer)
 void
 CoreAudioBackend::midi_clear (void* port_buffer)
 {
-	if (port_buffer) return;
+	if (!port_buffer) return;
 	CoreMidiBuffer * buf = static_cast<CoreMidiBuffer*>(port_buffer);
 	assert (buf);
 	buf->clear ();