diff --git a/distrho/DistrhoUI.hpp b/distrho/DistrhoUI.hpp
index 811d83ef..8dda7fae 100644
--- a/distrho/DistrhoUI.hpp
+++ b/distrho/DistrhoUI.hpp
@@ -303,17 +303,26 @@ protected:
     */
     virtual void uiFileBrowserSelected(const char* filename);
 # endif
+#endif // !DISTRHO_PLUGIN_HAS_EXTERNAL_UI
 
    /* --------------------------------------------------------------------------------------------------------
     * UI Resize Handling, internal */
 
+#if DISTRHO_PLUGIN_HAS_EXTERNAL_UI
+   /**
+      External Window resize function, called when the window is resized.
+      This is overriden here so the host knows when the UI is resized by you.
+      @see ExternalWindow::sizeChanged(uint,uint)
+    */
+    void sizeChanged(uint width, uint height) override;
+#else
    /**
-      OpenGL widget resize function, called when the widget is resized.
+      Widget resize function, called when the widget is resized.
       This is overriden here so the host knows when the UI is resized by you.
       @see Widget::onResize(const ResizeEvent&)
     */
     void onResize(const ResizeEvent& ev) override;
-#endif // !DISTRHO_PLUGIN_HAS_EXTERNAL_UI
+#endif
 
     // -------------------------------------------------------------------------------------------------------
 
diff --git a/distrho/src/DistrhoUI.cpp b/distrho/src/DistrhoUI.cpp
index 2dfb1d63..752b9cda 100644
--- a/distrho/src/DistrhoUI.cpp
+++ b/distrho/src/DistrhoUI.cpp
@@ -209,10 +209,19 @@ void UI::uiFileBrowserSelected(const char*)
 {
 }
 # endif
+#endif // !DISTRHO_PLUGIN_HAS_EXTERNAL_UI
 
 /* ------------------------------------------------------------------------------------------------------------
  * UI Resize Handling, internal */
 
+#if DISTRHO_PLUGIN_HAS_EXTERNAL_UI
+void UI::sizeChanged(const uint width, const uint height)
+{
+    UIWidget::sizeChanged(width, height);
+
+    uiData->setSizeCallback(width, height);
+}
+#else
 void UI::onResize(const ResizeEvent& ev)
 {
     UIWidget::onResize(ev);
@@ -221,7 +230,7 @@ void UI::onResize(const ResizeEvent& ev)
     const uint height = ev.size.getHeight();
     uiData->setSizeCallback(width, height);
 }
-#endif // !DISTRHO_PLUGIN_HAS_EXTERNAL_UI
+#endif
 
 // -----------------------------------------------------------------------------------------------------------