diff --git a/tests/suites/test_suite_ssl.function b/tests/suites/test_suite_ssl.function
index ef8d3b269d18..d9261d1a2acf 100644
--- a/tests/suites/test_suite_ssl.function
+++ b/tests/suites/test_suite_ssl.function
@@ -2649,7 +2649,7 @@ exit:
 void ssl_message_mock_uninitialized( )
 {
     enum { MSGLEN = 10 };
-    unsigned char message[MSGLEN], received[MSGLEN];
+    unsigned char message[MSGLEN] = {0}, received[MSGLEN];
     mbedtls_mock_socket client, server;
     mbedtls_test_message_queue server_queue, client_queue;
     mbedtls_test_message_socket_context server_context, client_context;