diff --git a/gst-libs/gst/pbutils/codec-utils.c b/gst-libs/gst/pbutils/codec-utils.c
index 228dd3cee6..3648ab76c9 100644
--- a/gst-libs/gst/pbutils/codec-utils.c
+++ b/gst-libs/gst/pbutils/codec-utils.c
@@ -1164,7 +1164,7 @@ gst_codec_utils_mpeg4video_caps_set_level_and_profile (GstCaps * caps,
  * @channel_mapping_family: (out): the channel mapping family
  * @stream_count: (out): the number of independent streams
  * @coupled_count: (out): the number of stereo streams
- * @channel_mapping: (out) (array): the mapping between the streams
+ * @channel_mapping: (out) (array fixed-size=256): the mapping between the streams
  *
  * Parses Opus caps and fills the different fields with defaults if possible.
  *
@@ -1585,7 +1585,7 @@ gst_codec_utils_opus_create_header (guint32 rate,
  * @channel_mapping_family: (out): the channel mapping family
  * @stream_count: (out): the number of independent streams
  * @coupled_count: (out): the number of stereo streams
- * @channel_mapping: (out) (array): the mapping between the streams
+ * @channel_mapping: (out) (array fixed-size=256): the mapping between the streams
  * @pre_skip: (out): Pre-skip in 48kHz samples or 0
  * @output_gain: (out): Output gain or 0
  *