diff --git a/sys/osxaudio/gstosxaudioringbuffer.c b/sys/osxaudio/gstosxaudioringbuffer.c
index 4677836bcb..d904b092b0 100644
--- a/sys/osxaudio/gstosxaudioringbuffer.c
+++ b/sys/osxaudio/gstosxaudioringbuffer.c
@@ -229,7 +229,10 @@ gst_osx_audio_ring_buffer_acquire (GstAudioRingBuffer * buf,
       CORE_AUDIO_FORMAT_ARGS (format));
 
   osxsink = GST_OSX_AUDIO_SINK (GST_OBJECT_PARENT (buf));
-  gst_audio_ring_buffer_set_channel_positions (buf, osxsink->channel_positions);
+  if (GST_IS_OSX_AUDIO_SINK (osxsink)) {
+    gst_audio_ring_buffer_set_channel_positions (buf,
+        osxsink->channel_positions);
+  }
 
   buf->size = spec->segtotal * spec->segsize;
   buf->memory = g_malloc0 (buf->size);
diff --git a/sys/osxaudio/gstosxaudiosink.h b/sys/osxaudio/gstosxaudiosink.h
index ad4838446e..84949b7fc4 100644
--- a/sys/osxaudio/gstosxaudiosink.h
+++ b/sys/osxaudio/gstosxaudiosink.h
@@ -63,6 +63,8 @@ G_BEGIN_DECLS
   (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_OSX_AUDIO_SINK,GstOsxAudioSink))
 #define GST_OSX_AUDIO_SINK_CLASS(klass) \
   (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_OSX_AUDIO_SINK,GstOsxAudioSinkClass))
+#define GST_IS_OSX_AUDIO_SINK(obj) \
+  (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_OSX_AUDIO_SINK))
 
 #define GST_OSX_AUDIO_MAX_CHANNEL (9)