diff --git a/gtk/theme/HighContrast/_common.scss b/gtk/theme/HighContrast/_common.scss
index caeb73a9b8..50b082afe6 100644
--- a/gtk/theme/HighContrast/_common.scss
+++ b/gtk/theme/HighContrast/_common.scss
@@ -421,7 +421,8 @@ button {
       }
     }
 
-    &:hover {
+    &:hover,
+    &.flat:hover {
       @include button(hover);
       -gtk-icon-effect: highlight;
     }
diff --git a/gtk/theme/HighContrast/gtk-contained-inverse.css b/gtk/theme/HighContrast/gtk-contained-inverse.css
index 1e58466ee0..66e196c492 100644
--- a/gtk/theme/HighContrast/gtk-contained-inverse.css
+++ b/gtk/theme/HighContrast/gtk-contained-inverse.css
@@ -178,7 +178,7 @@ button.sidebar-button:hover:active, button.titlebutton:hover:active, button.flat
 
 button.sidebar-button:backdrop, button.titlebutton:backdrop, button.sidebar-button:disabled, button.titlebutton:disabled, button.sidebar-button:backdrop:disabled, button.titlebutton:backdrop:disabled, button.flat:backdrop, button.flat:disabled, button.flat:backdrop:disabled { border-width: 2px; border-style: solid; color: gray; background-color: transparent; background-image: none; border-color: transparent; }
 
-button.titlebutton:hover, button:hover { border-width: 2px; border-style: solid; color: #fff; background-color: #000; border-color: gray; background-image: none; -gtk-icon-effect: highlight; }
+button.titlebutton:hover, button.sidebar-button:hover, button.titlebutton:hover, button:hover, button.flat:hover { border-width: 2px; border-style: solid; color: #fff; background-color: #000; border-color: gray; background-image: none; -gtk-icon-effect: highlight; }
 
 button.titlebutton:active, button.titlebutton:checked, button:active, button:checked { border-width: 2px; border-style: solid; background-image: none; color: black; background-color: white; border-color: gray; transition-duration: 50ms; }
 
diff --git a/gtk/theme/HighContrast/gtk-contained.css b/gtk/theme/HighContrast/gtk-contained.css
index a2d5fff7b9..e818e27632 100644
--- a/gtk/theme/HighContrast/gtk-contained.css
+++ b/gtk/theme/HighContrast/gtk-contained.css
@@ -178,7 +178,7 @@ button.sidebar-button:hover:active, button.titlebutton:hover:active, button.flat
 
 button.sidebar-button:backdrop, button.titlebutton:backdrop, button.sidebar-button:disabled, button.titlebutton:disabled, button.sidebar-button:backdrop:disabled, button.titlebutton:backdrop:disabled, button.flat:backdrop, button.flat:disabled, button.flat:backdrop:disabled { border-width: 2px; border-style: solid; color: gray; background-color: transparent; background-image: none; border-color: transparent; }
 
-button.titlebutton:hover, button:hover { border-width: 2px; border-style: solid; color: #000; background-color: #fff; border-color: gray; background-image: none; -gtk-icon-effect: highlight; }
+button.titlebutton:hover, button.sidebar-button:hover, button.titlebutton:hover, button:hover, button.flat:hover { border-width: 2px; border-style: solid; color: #000; background-color: #fff; border-color: gray; background-image: none; -gtk-icon-effect: highlight; }
 
 button.titlebutton:active, button.titlebutton:checked, button:active, button:checked { border-width: 2px; border-style: solid; background-image: none; color: white; background-color: black; border-color: gray; transition-duration: 50ms; }