diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index fa6d232..5acdbd5 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1628,6 +1628,13 @@
  *                     progress, this function will attempt to complete
  *                     the handshake first.
  *
+ * \note               If CID extensions have been exchanged but both client
+ *                     and server chose to use an empty CID, this function
+ *                     sets `*enabled` to #MBEDTLS_SSL_CID_DISABLED
+ *                     (the rationale for this is that the resulting
+ *                     communication is the same as if the CID extensions
+ *                     hadn't been used).
+ *
  * \return            \c 0 on success.
  * \return            A negative error code on failure.
  */
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index a0f9584..5cb15f5 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -165,11 +165,10 @@
     if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER )
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
 
-    /* What shall we report if we have exchanged if both client
-     * and server have used the CID extension, but negotiated
-     * empty CIDs? This is indistinguishable from not using the
-     * CID extension in the first place, and we're reporting
-     * MBEDTLS_SSL_CID_DISABLED in this case. */
+    /* We report MBEDTLS_SSL_CID_DISABLED in case the CID extensions
+     * were used, but client and server requested the empty CID.
+     * This is indistinguishable from not using the CID extension
+     * in the first place. */
     if( ssl->transform_in->in_cid_len  == 0 &&
         ssl->transform_in->out_cid_len == 0 )
     {