diff --git a/gtk-3.0/_common.scss b/gtk-3.0/_common.scss
index 8f98310f..86ad17fa 100644
--- a/gtk-3.0/_common.scss
+++ b/gtk-3.0/_common.scss
@@ -2044,58 +2044,46 @@ notebook {
 
     &.top {
       > stack { border-top-style: none; }
-      > tabs {
-        margin-bottom: -2px;
-        > tab {
-          border-radius: 3px 3px 0 0;
-          border: 1px solid shade($bg_color, 0.9);
+      > tabs > tab {
+        border-radius: 3px 3px 0 0;
+        border: 1px solid shade($bg_color, 0.9);
 
-          &:backdrop { box-shadow: none; }
+        &:backdrop { box-shadow: none; }
 
-          &:checked { border-width: 1px 1px 0 1px; }
-        }
+        &:checked { border-width: 1px 1px 0 1px; }
       }
     }
 
     &.bottom {
       > stack { border-bottom-style: none; }
-      > tabs {
-        margin-top: -2px;
-        > tab {
-          border-radius: 0 0 3px 3px;
+      > tabs > tab {
+        border-radius: 0 0 3px 3px;
 
-          &:backdrop { box-shadow: none; }
+        &:backdrop { box-shadow: none; }
 
-          &:checked { border-width: 0 1px 1px 1px; }
-        }
+        &:checked { border-width: 0 1px 1px 1px; }
       }
     }
 
     &.left {
       > stack { border-left-style: none; }
-      > tabs {
-        margin-right: -2px;
-        > tab {
-          border-radius: 3px 0 0 3px;
+      > tabs > tab {
+        border-radius: 3px 0 0 3px;
 
-          &:backdrop { box-shadow: none; }
+        &:backdrop { box-shadow: none; }
 
-          &:checked { border-width: 1px 0 1px 1px; }
-        }
+        &:checked { border-width: 1px 0 1px 1px; }
       }
     }
 
     &.right {
       > stack { border-right-style: none; }
-      > tabs {
-        margin-left: -2px;
-        > tab {
-          border-radius: 0 3px 3px 0;
+      > tabs > tab {
+        border-radius: 0 3px 3px 0;
 
-          &:backdrop { box-shadow: none; }
+        &:backdrop { box-shadow: none; }
 
-          &:checked { border-width: 1px 1px 1px 0; }
-        }
+        &:checked { border-width: 1px 1px 1px 0; }
       }
     }
 
@@ -2287,11 +2275,31 @@ notebook {
     &.bottom tab { padding-top: 4px; }
   }
 
-  > stack:not(:only-child) { // the :not(:only-child) is for "hidden" notebooks
-    background-color: shade($bg_color, 1.05);
-    border: 1px solid shade($bg_color, 0.9);
+  &.frame {
+    > header {
+      &.top > tabs {
+        margin-bottom: -2px;
+      }
+
+      &.bottom > tabs {
+        margin-top: -2px;
+      }
+
+      &.left > tabs {
+        margin-right: -2px;
+      }
 
-    &:backdrop { background-color: $backdrop_bg_color; }
+      &.right > tabs {
+        margin-left: -2px;
+      }
+    }
+
+    > stack:not(:only-child) { // the :not(:only-child) is for "hidden" notebooks
+      background-color: shade($bg_color, 1.05);
+      border: 1px solid shade($bg_color, 0.9);
+
+      &:backdrop { background-color: $backdrop_bg_color; }
+    }
   }
 }
 
diff --git a/gtk-3.0/gtk-contained-dark.css b/gtk-3.0/gtk-contained-dark.css
index ee1db7e6..f3d775c7 100644
--- a/gtk-3.0/gtk-contained-dark.css
+++ b/gtk-3.0/gtk-contained-dark.css
@@ -2285,45 +2285,37 @@ notebook > header {
     margin: -1px; }
   notebook > header.top > stack {
     border-top-style: none; }
-  notebook > header.top > tabs {
-    margin-bottom: -2px; }
-    notebook > header.top > tabs > tab {
-      border-radius: 3px 3px 0 0;
-      border: 1px solid shade(#393f3f, 0.9); }
-      notebook > header.top > tabs > tab:backdrop {
-        box-shadow: none; }
-      notebook > header.top > tabs > tab:checked {
-        border-width: 1px 1px 0 1px; }
+  notebook > header.top > tabs > tab {
+    border-radius: 3px 3px 0 0;
+    border: 1px solid shade(#393f3f, 0.9); }
+    notebook > header.top > tabs > tab:backdrop {
+      box-shadow: none; }
+    notebook > header.top > tabs > tab:checked {
+      border-width: 1px 1px 0 1px; }
   notebook > header.bottom > stack {
     border-bottom-style: none; }
-  notebook > header.bottom > tabs {
-    margin-top: -2px; }
-    notebook > header.bottom > tabs > tab {
-      border-radius: 0 0 3px 3px; }
-      notebook > header.bottom > tabs > tab:backdrop {
-        box-shadow: none; }
-      notebook > header.bottom > tabs > tab:checked {
-        border-width: 0 1px 1px 1px; }
+  notebook > header.bottom > tabs > tab {
+    border-radius: 0 0 3px 3px; }
+    notebook > header.bottom > tabs > tab:backdrop {
+      box-shadow: none; }
+    notebook > header.bottom > tabs > tab:checked {
+      border-width: 0 1px 1px 1px; }
   notebook > header.left > stack {
     border-left-style: none; }
-  notebook > header.left > tabs {
-    margin-right: -2px; }
-    notebook > header.left > tabs > tab {
-      border-radius: 3px 0 0 3px; }
-      notebook > header.left > tabs > tab:backdrop {
-        box-shadow: none; }
-      notebook > header.left > tabs > tab:checked {
-        border-width: 1px 0 1px 1px; }
+  notebook > header.left > tabs > tab {
+    border-radius: 3px 0 0 3px; }
+    notebook > header.left > tabs > tab:backdrop {
+      box-shadow: none; }
+    notebook > header.left > tabs > tab:checked {
+      border-width: 1px 0 1px 1px; }
   notebook > header.right > stack {
     border-right-style: none; }
-  notebook > header.right > tabs {
-    margin-left: -2px; }
-    notebook > header.right > tabs > tab {
-      border-radius: 0 3px 3px 0; }
-      notebook > header.right > tabs > tab:backdrop {
-        box-shadow: none; }
-      notebook > header.right > tabs > tab:checked {
-        border-width: 1px 1px 1px 0; }
+  notebook > header.right > tabs > tab {
+    border-radius: 0 3px 3px 0; }
+    notebook > header.right > tabs > tab:backdrop {
+      box-shadow: none; }
+    notebook > header.right > tabs > tab:checked {
+      border-width: 1px 1px 1px 0; }
   notebook > header.top > tabs > arrow {
     border-top-style: none; }
   notebook > header.bottom > tabs > arrow {
@@ -2446,10 +2438,18 @@ notebook > header {
     padding-bottom: 4px; }
   notebook > header.bottom tab {
     padding-top: 4px; }
-notebook > stack:not(:only-child) {
+notebook.frame > header.top > tabs {
+  margin-bottom: -2px; }
+notebook.frame > header.bottom > tabs {
+  margin-top: -2px; }
+notebook.frame > header.left > tabs {
+  margin-right: -2px; }
+notebook.frame > header.right > tabs {
+  margin-left: -2px; }
+notebook.frame > stack:not(:only-child) {
   background-color: shade(#393f3f, 1.05);
   border: 1px solid shade(#393f3f, 0.9); }
-  notebook > stack:not(:only-child):backdrop {
+  notebook.frame > stack:not(:only-child):backdrop {
     background-color: #393f3f; }
 
 /**************
diff --git a/gtk-3.0/gtk-contained.css b/gtk-3.0/gtk-contained.css
index 88ba7565..b42732a2 100644
--- a/gtk-3.0/gtk-contained.css
+++ b/gtk-3.0/gtk-contained.css
@@ -2298,45 +2298,37 @@ notebook > header {
     margin: -1px; }
   notebook > header.top > stack {
     border-top-style: none; }
-  notebook > header.top > tabs {
-    margin-bottom: -2px; }
-    notebook > header.top > tabs > tab {
-      border-radius: 3px 3px 0 0;
-      border: 1px solid shade(#cecece, 0.9); }
-      notebook > header.top > tabs > tab:backdrop {
-        box-shadow: none; }
-      notebook > header.top > tabs > tab:checked {
-        border-width: 1px 1px 0 1px; }
+  notebook > header.top > tabs > tab {
+    border-radius: 3px 3px 0 0;
+    border: 1px solid shade(#cecece, 0.9); }
+    notebook > header.top > tabs > tab:backdrop {
+      box-shadow: none; }
+    notebook > header.top > tabs > tab:checked {
+      border-width: 1px 1px 0 1px; }
   notebook > header.bottom > stack {
     border-bottom-style: none; }
-  notebook > header.bottom > tabs {
-    margin-top: -2px; }
-    notebook > header.bottom > tabs > tab {
-      border-radius: 0 0 3px 3px; }
-      notebook > header.bottom > tabs > tab:backdrop {
-        box-shadow: none; }
-      notebook > header.bottom > tabs > tab:checked {
-        border-width: 0 1px 1px 1px; }
+  notebook > header.bottom > tabs > tab {
+    border-radius: 0 0 3px 3px; }
+    notebook > header.bottom > tabs > tab:backdrop {
+      box-shadow: none; }
+    notebook > header.bottom > tabs > tab:checked {
+      border-width: 0 1px 1px 1px; }
   notebook > header.left > stack {
     border-left-style: none; }
-  notebook > header.left > tabs {
-    margin-right: -2px; }
-    notebook > header.left > tabs > tab {
-      border-radius: 3px 0 0 3px; }
-      notebook > header.left > tabs > tab:backdrop {
-        box-shadow: none; }
-      notebook > header.left > tabs > tab:checked {
-        border-width: 1px 0 1px 1px; }
+  notebook > header.left > tabs > tab {
+    border-radius: 3px 0 0 3px; }
+    notebook > header.left > tabs > tab:backdrop {
+      box-shadow: none; }
+    notebook > header.left > tabs > tab:checked {
+      border-width: 1px 0 1px 1px; }
   notebook > header.right > stack {
     border-right-style: none; }
-  notebook > header.right > tabs {
-    margin-left: -2px; }
-    notebook > header.right > tabs > tab {
-      border-radius: 0 3px 3px 0; }
-      notebook > header.right > tabs > tab:backdrop {
-        box-shadow: none; }
-      notebook > header.right > tabs > tab:checked {
-        border-width: 1px 1px 1px 0; }
+  notebook > header.right > tabs > tab {
+    border-radius: 0 3px 3px 0; }
+    notebook > header.right > tabs > tab:backdrop {
+      box-shadow: none; }
+    notebook > header.right > tabs > tab:checked {
+      border-width: 1px 1px 1px 0; }
   notebook > header.top > tabs > arrow {
     border-top-style: none; }
   notebook > header.bottom > tabs > arrow {
@@ -2459,10 +2451,18 @@ notebook > header {
     padding-bottom: 4px; }
   notebook > header.bottom tab {
     padding-top: 4px; }
-notebook > stack:not(:only-child) {
+notebook.frame > header.top > tabs {
+  margin-bottom: -2px; }
+notebook.frame > header.bottom > tabs {
+  margin-top: -2px; }
+notebook.frame > header.left > tabs {
+  margin-right: -2px; }
+notebook.frame > header.right > tabs {
+  margin-left: -2px; }
+notebook.frame > stack:not(:only-child) {
   background-color: shade(#cecece, 1.05);
   border: 1px solid shade(#cecece, 0.9); }
-  notebook > stack:not(:only-child):backdrop {
+  notebook.frame > stack:not(:only-child):backdrop {
     background-color: #cecece; }
 
 /**************