diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index 391ce5b..f9b0017 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -265,7 +265,7 @@
      */
     const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
                                         /*!<  Chosen cipersuite_info  */
-    unsigned int keylen;                /*!<  symmetric key length    */
+    unsigned int keylen;                /*!<  symmetric key length (bytes)  */
     size_t minlen;                      /*!<  min. ciphertext length  */
     size_t ivlen;                       /*!<  IV length               */
     size_t fixed_ivlen;                 /*!<  Fixed part of IV (AEAD) */