diff --git a/src/plugins/qmldesigner/components/toolbar/toolbarbackend.cpp b/src/plugins/qmldesigner/components/toolbar/toolbarbackend.cpp
index 3e406615c46..e77bd51d3b9 100644
--- a/src/plugins/qmldesigner/components/toolbar/toolbarbackend.cpp
+++ b/src/plugins/qmldesigner/components/toolbar/toolbarbackend.cpp
@@ -43,6 +43,8 @@ static Internal::DesignModeWidget *designModeWidget()
 
 static DesignDocument *currentDesignDocument()
 {
+    QTC_ASSERT(QmlDesignerPlugin::instance(), return nullptr);
+
     return QmlDesignerPlugin::instance()->documentManager().currentDesignDocument();
 }