diff --git a/components/style/gecko/media_features.rs b/components/style/gecko/media_features.rs
index e18b1cd8be6..b6596c75de8 100644
--- a/components/style/gecko/media_features.rs
+++ b/components/style/gecko/media_features.rs
@@ -526,7 +526,7 @@ lazy_static! {
     /// to support new types in these entries and (2) ensuring that either
     /// nsPresContext::MediaFeatureValuesChanged is called when the value that
     /// would be returned by the evaluator function could change.
-    pub static ref MEDIA_FEATURES: [MediaFeatureDescription; 51] = [
+    pub static ref MEDIA_FEATURES: [MediaFeatureDescription; 52] = [
         feature!(
             atom!("width"),
             AllowsRanges::Yes,
@@ -724,6 +724,7 @@ lazy_static! {
         system_metric_feature!(atom!("-moz-gtk-csd-minimize-button")),
         system_metric_feature!(atom!("-moz-gtk-csd-maximize-button")),
         system_metric_feature!(atom!("-moz-gtk-csd-close-button")),
+        system_metric_feature!(atom!("-moz-gtk-csd-reversed-placement")),
         system_metric_feature!(atom!("-moz-system-dark-theme")),
         // This is the only system-metric media feature that's accessible to
         // content as of today.