diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 70a9740..ac03884 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1780,6 +1780,13 @@
 #define MBEDTLS_SSL_TRUNCATED_HMAC
 
 /**
+ * \def MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH
+ *
+ * Enable modifying the maximum I/O buffer size.
+ */
+//#define MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH
+
+/**
  * \def MBEDTLS_SSL_TRUNCATED_HMAC_COMPAT
  *
  * Fallback to old (pre-2.7), non-conforming implementation of the truncated