diff --git a/components/style/gecko/values.rs b/components/style/gecko/values.rs
index 79cfcbb0beb..5260adbb10f 100644
--- a/components/style/gecko/values.rs
+++ b/components/style/gecko/values.rs
@@ -51,6 +51,19 @@ impl GeckoStyleCoordConvertible for LengthOrPercentage {
     }
 }
 
+impl GeckoStyleCoordConvertible for Au {
+    fn to_gecko_style_coord<T: CoordDataMut>(&self, coord: &mut T) {
+        coord.set_value(CoordDataValue::Coord(self.0));
+    }
+
+    fn from_gecko_style_coord<T: CoordData>(coord: &T) -> Option<Self> {
+        match coord.as_value() {
+            CoordDataValue::Coord(coord) => Some(Au(coord)),
+            _ => None,
+        }
+    }
+}
+
 impl GeckoStyleCoordConvertible for LengthOrPercentageOrAuto {
     fn to_gecko_style_coord<T: CoordDataMut>(&self, coord: &mut T) {
         let value = match *self {
diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index 5c6b40489c5..dd33495eb95 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -1837,7 +1837,7 @@ clip-path
 
     pub fn set_column_width(&mut self, v: longhands::column_width::computed_value::T) {
         match v.0 {
-            Some(au) => self.gecko.mColumnWidth.set_value(CoordDataValue::Coord(au.0)),
+            Some(au) => self.gecko.mColumnWidth.set(au),
             None => self.gecko.mColumnWidth.set_value(CoordDataValue::Auto),
         }
     }