diff --git a/tests/suites/test_suite_md.function b/tests/suites/test_suite_md.function
index d918ce3..8cbdbe4 100644
--- a/tests/suites/test_suite_md.function
+++ b/tests/suites/test_suite_md.function
@@ -16,6 +16,7 @@
     unsigned char buf[150];
 
     mbedtls_md_init( &ctx );
+    memset( buf, 0, sizeof( buf ) );
 
     /*
      * Very minimal testing of mbedtls_md_process, just make sure the various