diff --git a/cli/tests/application.cpp b/cli/tests/application.cpp
index 3571fcf..3c3d2a7 100644
--- a/cli/tests/application.cpp
+++ b/cli/tests/application.cpp
@@ -177,7 +177,11 @@ void ApplicationTests::test()
 
     // use environment variables to specify API-key and URL
     qputenv("SYNCTHING_CTL_API_KEY", apiKey);
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
     qputenv("SYNCTHING_CTL_URL", url);
+#else
+    qputenv("SYNCTHING_CTL_URL", QByteArray(url.data(), static_cast<int>(url.size())));
+#endif
 
     // test resume, verify via status for dirs only
     const char *const resumeArgs[] = { "syncthingctl", "resume", "--dir", "test2", nullptr };