diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 5fc136dff..dae455870 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1415,8 +1415,8 @@ void mbedtls_ssl_set_bio( mbedtls_ssl_context *ssl,
 
 
 /**
- * \brief             Configure the use of the Connection ID (CID) extension
- *                    in the next handshake.
+ * \brief             (STUB) Configure the use of the Connection ID (CID)
+ *                    extension in the next handshake.
  *
  *                    Reference:
  *                    https://tools.ietf.org/html/draft-ietf-tls-dtls-connection-id-04
@@ -1439,6 +1439,11 @@ void mbedtls_ssl_set_bio( mbedtls_ssl_context *ssl,
  *                    extension in the next handshake and to set the value of
  *                    the CID to be used for incoming messages.
  *
+ * \warning           The current implementation of this API does nothing!
+ *                    It is included solely to allow review and coding against
+ *                    the new Connection CID API.
+ *                    The actual implementation will be added in the future.
+ *
  * \param ssl         The SSL context to configure. This must be initialized.
  * \param enable      This value determines whether the CID extension should
  *                    be used or not. Possible values are:
@@ -1498,9 +1503,15 @@ int mbedtls_ssl_set_cid( mbedtls_ssl_context *ssl,
                          size_t own_cid_len );
 
 /**
- * \brief              Get information about the current use of the
+ * \brief              (STUB) Get information about the current use of the
  *                     CID extension.
  *
+ * \warning            The current implementation of this API does nothing
+ *                     except setting `*enabled` to MBEDTLS_SSL_CID_DISABLED!
+ *                     It is included solely to allow review and coding against
+ *                     the new Connection CID API.
+ *                     The actual implementation will be added in the future.
+ *
  * \param ssl          The SSL context to query.
  * \param enabled      The address at which to store whether the CID extension
  *                     is currently in use or not. If the CID is in use,
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index f9b3ad136..71ef949ea 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -111,6 +111,9 @@ static void ssl_update_in_pointers( mbedtls_ssl_context *ssl,
 
 /* Top-level Connection ID API */
 
+/* WARNING: This implementation is a stub and doesn't do anything!
+ *          It is included solely to allow review and coding against
+ *          the new Connection CID API. */
 int mbedtls_ssl_set_cid( mbedtls_ssl_context *ssl,
                          int enable,
                          unsigned char const *own_cid,
@@ -123,6 +126,9 @@ int mbedtls_ssl_set_cid( mbedtls_ssl_context *ssl,
     return( 0 );
 }
 
+/* WARNING: This implementation is a stub and doesn't do anything!
+ *          It is included solely to allow review and coding against
+ *          the new Connection CID API. */
 int mbedtls_ssl_get_peer_cid( mbedtls_ssl_context *ssl,
                      int *enabled,
                      unsigned char peer_cid[ MBEDTLS_SSL_CID_OUT_LEN_MAX ],