diff --git a/config.h.in b/config.h.in
index 05098ecb..f5ab8d9c 100644
--- a/config.h.in
+++ b/config.h.in
@@ -310,6 +310,9 @@
 /* Use PolarSSL library */
 #undef USE_CRYPTO_POLARSSL
 
+/* Use mbed TLS library */
+#undef USE_CRYPTO_MBEDTLS
+
 /* Version number of package */
 #undef VERSION