diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index 6158850..8acc377 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -523,6 +523,25 @@
 //#define MBEDTLS_AES_FEWER_TABLES
 
 /**
+ * \def MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH
+ *
+ * Use only 128-bit keys in AES operations to save ROM.
+ *
+ * Uncommenting this macro removes support for AES operations that are using 192
+ * or 256-bit keys.
+ *
+ * Tradeoff: Uncommenting this macro reduces ROM footprint by ~1116 bytes.
+ *
+ * If uncommented, uncomment also MBEDTLS_CTR_DRBG_USE_128_BIT_KEY
+ *
+ * Module:  library/aes.c
+ *
+ * Requires: MBEDTLS_AES_C
+ *
+ */
+//#define MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH
+
+/**
  * \def MBEDTLS_CAMELLIA_SMALL_MEMORY
  *
  * Use less ROM for the Camellia implementation (saves about 768 bytes).