diff --git a/components/style/gecko/media_features.rs b/components/style/gecko/media_features.rs
index a559adbcb1a..8c93dfa24ce 100644
--- a/components/style/gecko/media_features.rs
+++ b/components/style/gecko/media_features.rs
@@ -586,7 +586,7 @@ macro_rules! bool_pref_feature {
 /// 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 MEDIA_FEATURES: [QueryFeatureDescription; 60] = [
+pub static MEDIA_FEATURES: [QueryFeatureDescription; 59] = [
     feature!(
         atom!("width"),
         AllowsRanges::Yes,
@@ -855,10 +855,6 @@ pub static MEDIA_FEATURES: [QueryFeatureDescription; 60] = [
         ScrollArrowStyle,
         get_scrollbar_end_forward
     ),
-    lnf_int_feature!(
-        atom!("-moz-scrollbar-thumb-proportional"),
-        ScrollSliderStyle
-    ),
     lnf_int_feature!(atom!("-moz-menubar-drag"), MenuBarDrag),
     lnf_int_feature!(atom!("-moz-windows-default-theme"), WindowsDefaultTheme),
     lnf_int_feature!(atom!("-moz-mac-graphite-theme"), MacGraphiteTheme),