diff --git a/.config/niri/config.kdl b/.config/niri/config.kdl
index feedc8a3..2b1c7073 100644
--- a/.config/niri/config.kdl
+++ b/.config/niri/config.kdl
@@ -197,7 +197,9 @@ window-rule {
 }
 window-rule {
     match app-id="thunderbird$"
-    default-column-width { proportion 0.75; }
+    default-column-width {
+        proportion 0.75
+    }
 }
 window-rule {
     match app-id="vesktop$"
@@ -207,6 +209,9 @@ window-rule {
 }
 window-rule {
     match app-id="firefox$"
+    default-column-width {
+        proportion 0.66667
+    }
     clip-to-geometry true
 }
 // Open the Firefox picture-in-picture player as floating by default.