diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index 30dbf9386a..4fd2df2dac 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -1625,10 +1625,10 @@ headerbar {
 }
 
 headerbar { // headerbar border rounding
-  window:not(.tiled):not(.maximized):not(.solid-csd) separator:first-child + &, // tackles the paned container case
-  window:not(.tiled):not(.maximized):not(.solid-csd) &:first-child { &:backdrop, & { border-top-left-radius: 7px; }}
-  window:not(.tiled):not(.maximized):not(.solid-csd) &:last-child { &:backdrop, & { border-top-right-radius: 7px; }}
-  window:not(.tiled):not(.maximized):not(.solid-csd) stack & { // tackles the stacked headerbars case
+  window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) separator:first-child + &, // tackles the paned container case
+  window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) &:first-child { &:backdrop, & { border-top-left-radius: 7px; }}
+  window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) &:last-child { &:backdrop, & { border-top-right-radius: 7px; }}
+  window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) stack & { // tackles the stacked headerbars case
     &:first-child, &:last-child {
       &:backdrop, & {
         border-top-left-radius: 7px;
diff --git a/gtk/theme/Adwaita/gtk-contained-dark.css b/gtk/theme/Adwaita/gtk-contained-dark.css
index 5f06325a0d..e972c47bb8 100644
--- a/gtk/theme/Adwaita/gtk-contained-dark.css
+++ b/gtk/theme/Adwaita/gtk-contained-dark.css
@@ -662,11 +662,11 @@ headerbar switch { margin-top: 9px; margin-bottom: 9px; }
 
 .background:not(.tiled):not(.maximized):not(.solid-csd) .titlebar:backdrop, .background:not(.tiled):not(.maximized):not(.solid-csd) .titlebar { border-top-left-radius: 7px; border-top-right-radius: 7px; }
 
-window:not(.tiled):not(.maximized):not(.solid-csd) separator:first-child + headerbar:backdrop, window:not(.tiled):not(.maximized):not(.solid-csd) separator:first-child + headerbar, window:not(.tiled):not(.maximized):not(.solid-csd) headerbar:first-child:backdrop, window:not(.tiled):not(.maximized):not(.solid-csd) headerbar:first-child { border-top-left-radius: 7px; }
+window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) separator:first-child + headerbar:backdrop, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) separator:first-child + headerbar, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) headerbar:first-child:backdrop, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) headerbar:first-child { border-top-left-radius: 7px; }
 
-window:not(.tiled):not(.maximized):not(.solid-csd) headerbar:last-child:backdrop, window:not(.tiled):not(.maximized):not(.solid-csd) headerbar:last-child { border-top-right-radius: 7px; }
+window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) headerbar:last-child:backdrop, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) headerbar:last-child { border-top-right-radius: 7px; }
 
-window:not(.tiled):not(.maximized):not(.solid-csd) stack headerbar:first-child:backdrop, window:not(.tiled):not(.maximized):not(.solid-csd) stack headerbar:first-child, window:not(.tiled):not(.maximized):not(.solid-csd) stack headerbar:last-child:backdrop, window:not(.tiled):not(.maximized):not(.solid-csd) stack headerbar:last-child { border-top-left-radius: 7px; border-top-right-radius: 7px; }
+window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) stack headerbar:first-child:backdrop, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) stack headerbar:first-child, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) stack headerbar:last-child:backdrop, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) stack headerbar:last-child { border-top-left-radius: 7px; border-top-right-radius: 7px; }
 
 window.csd > .titlebar:not(headerbar) { padding: 0; background-color: transparent; background-image: none; border-style: none; border-color: transparent; box-shadow: none; }
 
diff --git a/gtk/theme/Adwaita/gtk-contained.css b/gtk/theme/Adwaita/gtk-contained.css
index ac03d4b884..c85ca7b12d 100644
--- a/gtk/theme/Adwaita/gtk-contained.css
+++ b/gtk/theme/Adwaita/gtk-contained.css
@@ -670,11 +670,11 @@ headerbar switch { margin-top: 9px; margin-bottom: 9px; }
 
 .background:not(.tiled):not(.maximized):not(.solid-csd) .titlebar:backdrop, .background:not(.tiled):not(.maximized):not(.solid-csd) .titlebar { border-top-left-radius: 7px; border-top-right-radius: 7px; }
 
-window:not(.tiled):not(.maximized):not(.solid-csd) separator:first-child + headerbar:backdrop, window:not(.tiled):not(.maximized):not(.solid-csd) separator:first-child + headerbar, window:not(.tiled):not(.maximized):not(.solid-csd) headerbar:first-child:backdrop, window:not(.tiled):not(.maximized):not(.solid-csd) headerbar:first-child { border-top-left-radius: 7px; }
+window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) separator:first-child + headerbar:backdrop, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) separator:first-child + headerbar, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) headerbar:first-child:backdrop, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) headerbar:first-child { border-top-left-radius: 7px; }
 
-window:not(.tiled):not(.maximized):not(.solid-csd) headerbar:last-child:backdrop, window:not(.tiled):not(.maximized):not(.solid-csd) headerbar:last-child { border-top-right-radius: 7px; }
+window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) headerbar:last-child:backdrop, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) headerbar:last-child { border-top-right-radius: 7px; }
 
-window:not(.tiled):not(.maximized):not(.solid-csd) stack headerbar:first-child:backdrop, window:not(.tiled):not(.maximized):not(.solid-csd) stack headerbar:first-child, window:not(.tiled):not(.maximized):not(.solid-csd) stack headerbar:last-child:backdrop, window:not(.tiled):not(.maximized):not(.solid-csd) stack headerbar:last-child { border-top-left-radius: 7px; border-top-right-radius: 7px; }
+window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) stack headerbar:first-child:backdrop, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) stack headerbar:first-child, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) stack headerbar:last-child:backdrop, window:not(.tiled):not(.maximized):not(.fullscreen):not(.solid-csd) stack headerbar:last-child { border-top-left-radius: 7px; border-top-right-radius: 7px; }
 
 window.csd > .titlebar:not(headerbar) { padding: 0; background-color: transparent; background-image: none; border-style: none; border-color: transparent; box-shadow: none; }