diff --git a/demos/gtk-demo/blendmodes.ui b/demos/gtk-demo/blendmodes.ui
index 9badf330dc..02dc736503 100644
--- a/demos/gtk-demo/blendmodes.ui
+++ b/demos/gtk-demo/blendmodes.ui
@@ -3,6 +3,7 @@
   <requires lib="gtk+" version="3.20"/>
   <object class="GtkWindow" id="window">
     <property name="can_focus">False</property>
+    <property name="resizable">False</property>
     <property name="title">CSS Blend Modes</property>
     <property name="default_width">400</property>
     <property name="default_height">300</property>