diff --git a/gtk2_ardour/ui/editor_mixer.xml b/gtk2_ardour/ui/editor_mixer.xml
index 4c66a0d9b0..eeeca6eaa5 100644
--- a/gtk2_ardour/ui/editor_mixer.xml
+++ b/gtk2_ardour/ui/editor_mixer.xml
@@ -5,7 +5,7 @@
          gainmeterscript="inspector_gain_meter.xml">
   <HBox>
     <VBox>
-      <VBox>
+      <VBox box.fill="true" box.expand="true">
         <VBox id="color_palette_home"
               noshowall="true">
           <EventBox id="color_palette_button_home"