diff --git a/tests/filekind/filekind.cpp b/tests/filekind/filekind.cpp
index d94ad52fa7..1e4b55455b 100644
--- a/tests/filekind/filekind.cpp
+++ b/tests/filekind/filekind.cpp
@@ -175,7 +175,7 @@ void FileKindTestCase::SocketStream()
 //
 void FileKindTestCase::MemoryStream()
 {
-    char buf[20];
+    char buf[20] = { 0 };
     wxMemoryInputStream inStream(buf, sizeof(buf));
     CPPUNIT_ASSERT(inStream.IsSeekable());
     wxMemoryOutputStream outStream(buf, sizeof(buf));