diff --git a/scripts/config.pl b/scripts/config.pl
index e554969..cf766a8 100755
--- a/scripts/config.pl
+++ b/scripts/config.pl
@@ -51,6 +51,7 @@
 #   MBEDTLS_PKCS11_C
 #   MBEDTLS_NO_UDBL_DIVISION
 #   MBEDTLS_NO_64BIT_MULTIPLICATION
+#   MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH
 #   and any symbol beginning _ALT
 #
 
@@ -126,6 +127,7 @@
 MBEDTLS_NO_UDBL_DIVISION
 MBEDTLS_NO_64BIT_MULTIPLICATION
 MBEDTLS_USE_TINYCRYPT
+MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH
 _ALT\s*$
 );