diff --git a/src/plugins/qmldesigner/components/toolbar/toolbarbackend.cpp b/src/plugins/qmldesigner/components/toolbar/toolbarbackend.cpp
index 917a4f96dcd..d59c5218793 100644
--- a/src/plugins/qmldesigner/components/toolbar/toolbarbackend.cpp
+++ b/src/plugins/qmldesigner/components/toolbar/toolbarbackend.cpp
@@ -455,6 +455,9 @@ int ToolBarBackend::currentKit() const
 
 bool ToolBarBackend::isQt6() const
 {
+    if (!ProjectExplorer::SessionManager::startupTarget())
+        return false;
+
     const QmlProjectManager::QmlBuildSystem *buildSystem = qobject_cast<QmlProjectManager::QmlBuildSystem *>(
         ProjectExplorer::SessionManager::startupTarget()->buildSystem());
     QTC_ASSERT(buildSystem, return false);