diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index b80667a..43ca74e 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1137,7 +1137,7 @@
  * operation inside the library.
  *
  */
-//#define MBEDTLS_SSL_ASYNC_PRIVATE
+#define MBEDTLS_SSL_ASYNC_PRIVATE
 
 /**
  * \def MBEDTLS_SSL_DEBUG_ALL