diff --git a/src/main/gtk-3.0/gtk-dark-blue.css b/src/main/gtk-3.0/gtk-dark-blue.css
index 9068d9d4..584e8865 100644
--- a/src/main/gtk-3.0/gtk-dark-blue.css
+++ b/src/main/gtk-3.0/gtk-dark-blue.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-green.css b/src/main/gtk-3.0/gtk-dark-green.css
index 468f6545..0b214dd1 100644
--- a/src/main/gtk-3.0/gtk-dark-green.css
+++ b/src/main/gtk-3.0/gtk-dark-green.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-grey.css b/src/main/gtk-3.0/gtk-dark-grey.css
index 2c969a55..86faad31 100644
--- a/src/main/gtk-3.0/gtk-dark-grey.css
+++ b/src/main/gtk-3.0/gtk-dark-grey.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-orange.css b/src/main/gtk-3.0/gtk-dark-orange.css
index ccce8e34..d50e7a80 100644
--- a/src/main/gtk-3.0/gtk-dark-orange.css
+++ b/src/main/gtk-3.0/gtk-dark-orange.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-pink.css b/src/main/gtk-3.0/gtk-dark-pink.css
index de41e1c8..3d72d642 100644
--- a/src/main/gtk-3.0/gtk-dark-pink.css
+++ b/src/main/gtk-3.0/gtk-dark-pink.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-purple.css b/src/main/gtk-3.0/gtk-dark-purple.css
index f0107703..67514c25 100644
--- a/src/main/gtk-3.0/gtk-dark-purple.css
+++ b/src/main/gtk-3.0/gtk-dark-purple.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-red.css b/src/main/gtk-3.0/gtk-dark-red.css
index 6a17b486..a26898ee 100644
--- a/src/main/gtk-3.0/gtk-dark-red.css
+++ b/src/main/gtk-3.0/gtk-dark-red.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-solid-blue.css b/src/main/gtk-3.0/gtk-dark-solid-blue.css
index 310d4274..0efa7600 100644
--- a/src/main/gtk-3.0/gtk-dark-solid-blue.css
+++ b/src/main/gtk-3.0/gtk-dark-solid-blue.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-solid-green.css b/src/main/gtk-3.0/gtk-dark-solid-green.css
index 0d867fa1..9de51cd3 100644
--- a/src/main/gtk-3.0/gtk-dark-solid-green.css
+++ b/src/main/gtk-3.0/gtk-dark-solid-green.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-solid-grey.css b/src/main/gtk-3.0/gtk-dark-solid-grey.css
index 404f7151..76141916 100644
--- a/src/main/gtk-3.0/gtk-dark-solid-grey.css
+++ b/src/main/gtk-3.0/gtk-dark-solid-grey.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-solid-orange.css b/src/main/gtk-3.0/gtk-dark-solid-orange.css
index 1a0153ca..1d131a5b 100644
--- a/src/main/gtk-3.0/gtk-dark-solid-orange.css
+++ b/src/main/gtk-3.0/gtk-dark-solid-orange.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-solid-pink.css b/src/main/gtk-3.0/gtk-dark-solid-pink.css
index f8871433..46f54d38 100644
--- a/src/main/gtk-3.0/gtk-dark-solid-pink.css
+++ b/src/main/gtk-3.0/gtk-dark-solid-pink.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-solid-purple.css b/src/main/gtk-3.0/gtk-dark-solid-purple.css
index d73f7566..1227d915 100644
--- a/src/main/gtk-3.0/gtk-dark-solid-purple.css
+++ b/src/main/gtk-3.0/gtk-dark-solid-purple.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-solid-red.css b/src/main/gtk-3.0/gtk-dark-solid-red.css
index 75e1d46c..976b31ce 100644
--- a/src/main/gtk-3.0/gtk-dark-solid-red.css
+++ b/src/main/gtk-3.0/gtk-dark-solid-red.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-solid-yellow.css b/src/main/gtk-3.0/gtk-dark-solid-yellow.css
index 76949065..4c16f20c 100644
--- a/src/main/gtk-3.0/gtk-dark-solid-yellow.css
+++ b/src/main/gtk-3.0/gtk-dark-solid-yellow.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-solid.css b/src/main/gtk-3.0/gtk-dark-solid.css
index 3eee88c2..5818bf84 100644
--- a/src/main/gtk-3.0/gtk-dark-solid.css
+++ b/src/main/gtk-3.0/gtk-dark-solid.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark-yellow.css b/src/main/gtk-3.0/gtk-dark-yellow.css
index 0fa8a7f6..83ea466f 100644
--- a/src/main/gtk-3.0/gtk-dark-yellow.css
+++ b/src/main/gtk-3.0/gtk-dark-yellow.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-dark.css b/src/main/gtk-3.0/gtk-dark.css
index cad4dbf3..cb63bd87 100644
--- a/src/main/gtk-3.0/gtk-dark.css
+++ b/src/main/gtk-3.0/gtk-dark.css
@@ -1769,6 +1769,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-blue.css b/src/main/gtk-3.0/gtk-light-blue.css
index 4584fd96..5b5e0e36 100644
--- a/src/main/gtk-3.0/gtk-light-blue.css
+++ b/src/main/gtk-3.0/gtk-light-blue.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-green.css b/src/main/gtk-3.0/gtk-light-green.css
index 65517fd9..21187f9d 100644
--- a/src/main/gtk-3.0/gtk-light-green.css
+++ b/src/main/gtk-3.0/gtk-light-green.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-grey.css b/src/main/gtk-3.0/gtk-light-grey.css
index d7a295e6..868a536a 100644
--- a/src/main/gtk-3.0/gtk-light-grey.css
+++ b/src/main/gtk-3.0/gtk-light-grey.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-orange.css b/src/main/gtk-3.0/gtk-light-orange.css
index 6891d204..bba47907 100644
--- a/src/main/gtk-3.0/gtk-light-orange.css
+++ b/src/main/gtk-3.0/gtk-light-orange.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-pink.css b/src/main/gtk-3.0/gtk-light-pink.css
index 3ee1c962..42500b01 100644
--- a/src/main/gtk-3.0/gtk-light-pink.css
+++ b/src/main/gtk-3.0/gtk-light-pink.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-purple.css b/src/main/gtk-3.0/gtk-light-purple.css
index ed9f0eaa..7480b24a 100644
--- a/src/main/gtk-3.0/gtk-light-purple.css
+++ b/src/main/gtk-3.0/gtk-light-purple.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-red.css b/src/main/gtk-3.0/gtk-light-red.css
index f7d096e7..696a0406 100644
--- a/src/main/gtk-3.0/gtk-light-red.css
+++ b/src/main/gtk-3.0/gtk-light-red.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-solid-blue.css b/src/main/gtk-3.0/gtk-light-solid-blue.css
index bc5fee78..95a90dda 100644
--- a/src/main/gtk-3.0/gtk-light-solid-blue.css
+++ b/src/main/gtk-3.0/gtk-light-solid-blue.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-solid-green.css b/src/main/gtk-3.0/gtk-light-solid-green.css
index b98e331f..7ecb38a8 100644
--- a/src/main/gtk-3.0/gtk-light-solid-green.css
+++ b/src/main/gtk-3.0/gtk-light-solid-green.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-solid-grey.css b/src/main/gtk-3.0/gtk-light-solid-grey.css
index a335b0e8..c03a49b5 100644
--- a/src/main/gtk-3.0/gtk-light-solid-grey.css
+++ b/src/main/gtk-3.0/gtk-light-solid-grey.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-solid-orange.css b/src/main/gtk-3.0/gtk-light-solid-orange.css
index a913440e..0c7c4e12 100644
--- a/src/main/gtk-3.0/gtk-light-solid-orange.css
+++ b/src/main/gtk-3.0/gtk-light-solid-orange.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-solid-pink.css b/src/main/gtk-3.0/gtk-light-solid-pink.css
index c20a422d..ee3dac9b 100644
--- a/src/main/gtk-3.0/gtk-light-solid-pink.css
+++ b/src/main/gtk-3.0/gtk-light-solid-pink.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-solid-purple.css b/src/main/gtk-3.0/gtk-light-solid-purple.css
index be1f5df8..41b3c1b9 100644
--- a/src/main/gtk-3.0/gtk-light-solid-purple.css
+++ b/src/main/gtk-3.0/gtk-light-solid-purple.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-solid-red.css b/src/main/gtk-3.0/gtk-light-solid-red.css
index f637ad9e..9d82d70b 100644
--- a/src/main/gtk-3.0/gtk-light-solid-red.css
+++ b/src/main/gtk-3.0/gtk-light-solid-red.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-solid-yellow.css b/src/main/gtk-3.0/gtk-light-solid-yellow.css
index fdd36e69..a16fbc23 100644
--- a/src/main/gtk-3.0/gtk-light-solid-yellow.css
+++ b/src/main/gtk-3.0/gtk-light-solid-yellow.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-solid.css b/src/main/gtk-3.0/gtk-light-solid.css
index f92cfe32..0b184399 100644
--- a/src/main/gtk-3.0/gtk-light-solid.css
+++ b/src/main/gtk-3.0/gtk-light-solid.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light-yellow.css b/src/main/gtk-3.0/gtk-light-yellow.css
index 2dae4d2c..53598cc9 100644
--- a/src/main/gtk-3.0/gtk-light-yellow.css
+++ b/src/main/gtk-3.0/gtk-light-yellow.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/main/gtk-3.0/gtk-light.css b/src/main/gtk-3.0/gtk-light.css
index b928cbc6..1dba31ab 100644
--- a/src/main/gtk-3.0/gtk-light.css
+++ b/src/main/gtk-3.0/gtk-light.css
@@ -1777,6 +1777,10 @@ window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop, w
   min-width: 1px;
 }
 
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar button, .titlebar button {
   min-height: 26px;
   min-width: 22px;
diff --git a/src/other/firefox/chrome/WhiteSur/rounded-window-maximized.css b/src/other/firefox/chrome/WhiteSur/rounded-window-maximized.css
index ff050992..87a66109 100644
--- a/src/other/firefox/chrome/WhiteSur/rounded-window-maximized.css
+++ b/src/other/firefox/chrome/WhiteSur/rounded-window-maximized.css
@@ -1,5 +1,5 @@
 @namespace xul url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 
-:root[tabsintitlebar]:not([inFullscreen]) #nav-bar {
+:root[tabsintitlebar]:not([inFullscreen])[sizemode="maximized"] #nav-bar {
 	border-radius: 16px 16px 0 0;
 }
diff --git a/src/sass/gtk/_common.scss b/src/sass/gtk/_common.scss
index 40afcdc1..52003bb4 100644
--- a/src/sass/gtk/_common.scss
+++ b/src/sass/gtk/_common.scss
@@ -1647,6 +1647,11 @@ window.background > box.vertical > headerbar:not(.titlebar) { // reset headerbar
   }
 }
 
+// Fixes common window border radius problem when it get maximized
+window.background.csd.maximized {
+  border-radius: 0px;
+}
+
 headerbar, .titlebar {
   button {
     min-height: 26px;