diff --git a/include/asterisk/mod_format.h b/include/asterisk/mod_format.h
index bcd31deaad48bc777d0e848169eba8c289522742..7e05a282b58b5c8e94ad5c9698de8cd04747dac5 100644
--- a/include/asterisk/mod_format.h
+++ b/include/asterisk/mod_format.h
@@ -114,7 +114,11 @@ struct ast_filestream {
 	int lasttimeout;
 	struct ast_channel *owner;
 	FILE *f;
-	struct ast_frame fr;	/*!< frame produced by read, typically */
+	/*!
+	 * \brief frame produced by read, typically
+	 * \note This frame holds a fr.subclass.format ref.
+	 */
+	struct ast_frame fr;
 	char *buf;		/*!< buffer pointed to by ast_frame; */
 	void *_private;	/*!< pointer to private buffer */
 	const char *orig_chan_name;
diff --git a/include/asterisk/translate.h b/include/asterisk/translate.h
index 8188eb8ebfec52a31d14c5749b0ee63f8b9689ef..5c7990945d2f19180906e16333c6cf9fa31d578d 100644
--- a/include/asterisk/translate.h
+++ b/include/asterisk/translate.h
@@ -208,7 +208,7 @@ struct ast_translator {
  */
 struct ast_trans_pvt {
 	struct ast_translator *t;
-	struct ast_frame f;         /*!< used in frameout */
+	struct ast_frame f;         /*!< used in frameout.  This frame holds a f.subclass.format ref. */
 	int samples;                /*!< samples available in outbuf */
 	/*! \brief actual space used in outbuf */
 	int datalen;