diff --git a/client/ayon_core/lib/transcoding.py b/client/ayon_core/lib/transcoding.py
index e665486d7b..57ae6cb0bc 100644
--- a/client/ayon_core/lib/transcoding.py
+++ b/client/ayon_core/lib/transcoding.py
@@ -68,7 +68,12 @@ VIDEO_EXTENSIONS = {
 
 
 class MissingRGBAChannelsError(ValueError):
-    """Raised when we can't find RGB channels for conversion in input media."""
+    """Raised when we can't find channels to use as RGBA for conversion in
+    input media.
+
+    This may be other channels than solely RGBA, like Z-channel. The error is
+    raised when no matching 'reviewable' channel was found.
+    """
     pass