diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 0f65133..e5e9a88 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -640,10 +640,13 @@
  * Add countermeasures against possible side-channel-attack to AES calculation.
  *
  * Uncommenting this macro adds additional calculation rounds to AES
- * calculation. Additional rounds are using random data and can occur in any
- * AES calculation round.
+ * calculation. Additional rounds are using random data for calculation. The
+ * additional rounds are added to:
+ * -initial key addition phase
+ * -before the first AES calculation round
+ * -after the last AES calculation round
  *
- * Tradeoff: Uncommenting this increases ROM footprint by ~100 bytes.
+ * Tradeoff: Uncommenting this macro does not increases ROM footprint.
  * The performance loss is ~50% with 128 bit AES.
  *
  * This option is dependent of \c MBEDTLS_ENTROPY_HARDWARE_ALT.