diff --git a/src/testlib/qabstracttestlogger.cpp b/src/testlib/qabstracttestlogger.cpp
index 9ac1de9909..7f0c70e975 100644
--- a/src/testlib/qabstracttestlogger.cpp
+++ b/src/testlib/qabstracttestlogger.cpp
@@ -93,6 +93,7 @@ void QAbstractTestLogger::filterUnprintable(char *str) const
 void QAbstractTestLogger::outputString(const char *msg)
 {
     QTEST_ASSERT(stream);
+    QTEST_ASSERT(msg);
 
     char *filtered = new char[strlen(msg) + 1];
     strcpy(filtered, msg);