diff --git a/src/Nonemm.App/App.axaml.cs b/src/Nonemm.App/App.axaml.cs
index 88d35d3..6c1834c 100644
--- a/src/Nonemm.App/App.axaml.cs
+++ b/src/Nonemm.App/App.axaml.cs
@@ -66,6 +66,8 @@ public partial class App : Application
         {
             Set(key, theme.FieldForeground);
         }
+        // the line under the selected tab, which the Fluent blue leaves faint on a dark form
+        Set("TabItemHeaderSelectedPipeFill", theme.FormForeground);
         Set("ButtonBackground", theme.ButtonBackground);
         Set("ButtonBackgroundPointerOver", Lighter(theme.ButtonBackground));
         Set("ButtonBackgroundPressed", Darker(theme.ButtonBackground));