diff --git a/gtk/theme/Default/_common.scss b/gtk/theme/Default/_common.scss
index 3c2edfcc98..88d1feaa37 100644
--- a/gtk/theme/Default/_common.scss
+++ b/gtk/theme/Default/_common.scss
@@ -2570,6 +2570,7 @@ radio {
     @each $state, $t in ("", "normal"),
                         (":hover", "hover"),
                         (":active", "active"),
+                        (":backdrop", "backdrop"),
                         (":disabled", "insensitive") {
       &#{$state} {
         @include check($t, $_c);
@@ -2584,6 +2585,7 @@ radio {
         @each $state, $t in ("", "normal"),
                             (":hover", "hover"),
                             (":active", "active"),
+                            (":backdrop", "backdrop"),
                             (":disabled", "insensitive") {
           &#{$state} {
             @include check($t, $checkradio_bg_color, $checkradio_fg_color, $checked: true);