diff --git a/src/controllers/Stack.cpp b/src/controllers/Stack.cpp
index 1d2d5085..429071dd 100644
--- a/src/controllers/Stack.cpp
+++ b/src/controllers/Stack.cpp
@@ -233,7 +233,9 @@ int Stack::currentIndex() const
 
 int Stack::numDockWidgets() const
 {
-    return dynamic_cast<Views::StackViewInterface *>(view())->numDockWidgets();
+    auto svi = dynamic_cast<Views::StackViewInterface *>(view());
+    Q_ASSERT(svi);
+    return svi->numDockWidgets();
 }
 
 void Stack::changeTabIcon(int index, const QIcon &icon)