diff --git a/gtk-3.0/gtk-dark.css b/gtk-3.0/gtk-dark.css
index 341bb20..815ac0d 100755
--- a/gtk-3.0/gtk-dark.css
+++ b/gtk-3.0/gtk-dark.css
@@ -3219,6 +3219,14 @@ notebook > stack:not(:only-child) {
   notebook > stack:not(:only-child):backdrop {
     background-color: #1a1d2b; }
 
+notebook button.flat {
+  padding: 2px 4px; }
+  notebook button.flat, notebook button.flat:backdrop {
+    border: none;
+    background-color: transparent; }
+  notebook button.flat:hover, notebook button.flat:active, notebook button.flat:checked {
+    background: #00D3A7; }
+
 /*********
  * Paned *
  *********/
diff --git a/gtk-3.0/gtk.css b/gtk-3.0/gtk.css
index e312dab..fe382cc 100755
--- a/gtk-3.0/gtk.css
+++ b/gtk-3.0/gtk.css
@@ -3226,6 +3226,14 @@ notebook > stack:not(:only-child) {
   notebook > stack:not(:only-child):backdrop {
     background-color: #e8edf3; }
 
+notebook button.flat {
+  padding: 2px 4px; }
+  notebook button.flat, notebook button.flat:backdrop {
+    border: none;
+    background-color: transparent; }
+  notebook button.flat:hover, notebook button.flat:active, notebook button.flat:checked {
+    background: #00D3A7; }
+
 /*********
  * Paned *
  *********/
diff --git a/gtk-3.0/widgets/_notebooks.scss b/gtk-3.0/widgets/_notebooks.scss
index 84304dc..6851d0f 100644
--- a/gtk-3.0/widgets/_notebooks.scss
+++ b/gtk-3.0/widgets/_notebooks.scss
@@ -209,7 +209,11 @@ notebook {
 
       // colors the button like the label, overridden otherwise
       button.flat {
-        &:hover {  background: transparent; box-shadow: none; color: $red; }
+        &:hover {  
+          background: transparent;
+          box-shadow: none;
+          color: $red; 
+        }
 
         &, &:backdrop { color: gtkalpha(currentColor, 0.3); }
 
@@ -292,4 +296,15 @@ notebook {
 
     &:backdrop { background-color: $backdrop_base_color; }
   }
+
+  button.flat{
+    &, &:backdrop {
+      border: none;
+      background-color: transparent;
+    }
+    &:hover, &:active, &:checked {
+      background: $selected_bg_color;
+    }
+    padding: 2px 4px;
+  }
 }