diff --git a/gtk2_ardour/themes/dark-ardour.colors b/gtk2_ardour/themes/dark-ardour.colors
index 16e5d86782..0de02ac83f 100644
--- a/gtk2_ardour/themes/dark-ardour.colors
+++ b/gtk2_ardour/themes/dark-ardour.colors
@@ -294,6 +294,7 @@
     <ColorAlias name="piano roll black" alias="theme:contrasting selection"/>
     <ColorAlias name="piano roll black outline" alias="neutral:foreground2"/>
     <ColorAlias name="piano roll white" alias="neutral:foreground2"/>
+    <ColorAlias name="piano roll offkey" alias="alert:ruddy"/>
     <ColorAlias name="pinrouting custom: led active" alias="alert:ruddy"/>
     <ColorAlias name="pinrouting sidechain: led active" alias="alert:green"/>
     <ColorAlias name="play head" alias="theme:contrasting"/>