diff --git a/gst-libs/gst/audio/gstaudiometa.c b/gst-libs/gst/audio/gstaudiometa.c
index 1a7e575692..f26e0d48c9 100644
--- a/gst-libs/gst/audio/gstaudiometa.c
+++ b/gst-libs/gst/audio/gstaudiometa.c
@@ -63,7 +63,8 @@ gst_audio_downmix_meta_transform (GstBuffer * dest, GstMeta * meta,
 /**
  * gst_buffer_get_audio_downmix_meta_for_channels:
  * @buffer: a #GstBuffer
- * @to_position: the channel positions of the destination
+ * @to_position: (array length=to_channels): the channel positions of
+ *   the destination
  * @to_channels: The number of channels of the destination
  *
  * Find the #GstAudioDownmixMeta on @buffer for the given destination
@@ -94,9 +95,11 @@ gst_buffer_get_audio_downmix_meta_for_channels (GstBuffer * buffer,
 /**
  * gst_buffer_add_audio_downmix_meta:
  * @buffer: a #GstBuffer
- * @from_position: the channel positions of the source
+ * @from_position: (array length=from_channels): the channel positions
+ *   of the source
  * @from_channels: The number of channels of the source
- * @to_position: the channel positions of the destination
+ * @to_position: (array length=to_channels): the channel positions of
+ *   the destination
  * @to_channels: The number of channels of the destination
  * @matrix: The matrix coefficients.
  *