diff --git a/ports/geckolib/properties.mako.rs b/ports/geckolib/properties.mako.rs
index 5ef6f45d568..75ef9c6215c 100644
--- a/ports/geckolib/properties.mako.rs
+++ b/ports/geckolib/properties.mako.rs
@@ -29,8 +29,8 @@ use style::properties::{CascadePropertyFn, ServoComputedValues, ComputedValues};
 use style::properties::longhands;
 use style::properties::make_cascade_vec;
 use style::properties::style_struct_traits::*;
-use values::{ToGeckoStyleCoord, convert_rgba_to_nscolor, convert_nscolor_to_rgba};
-use values::round_border_to_device_pixels;
+use values::{StyleCoordHelpers, ToGeckoStyleCoord, convert_nscolor_to_rgba};
+use values::{convert_rgba_to_nscolor, round_border_to_device_pixels};
 
 #[derive(Clone)]
 pub struct GeckoComputedValues {
@@ -552,17 +552,10 @@ fn static_assert() {
     % endfor
 
     fn set_z_index(&mut self, v: longhands::z_index::computed_value::T) {
-        use gecko_bindings::structs::nsStyleUnit;
         use style::properties::longhands::z_index::computed_value::T;
         match v {
-            T::Auto => {
-                self.gecko.mZIndex.mUnit = nsStyleUnit::eStyleUnit_Auto;
-                unsafe { *self.gecko.mZIndex.mValue.mInt.as_mut() = 0; }
-            }
-            T::Number(n) => {
-                self.gecko.mZIndex.mUnit = nsStyleUnit::eStyleUnit_Integer;
-                unsafe { *self.gecko.mZIndex.mValue.mInt.as_mut() = n; }
-            }
+            T::Auto => self.gecko.mZIndex.set_auto(),
+            T::Number(n) => self.gecko.mZIndex.set_int(n),
         }
     }
     fn copy_z_index_from(&mut self, other: &Self) {
diff --git a/ports/geckolib/values.rs b/ports/geckolib/values.rs
index 069fb9bc9b6..d9e6da0fd83 100644
--- a/ports/geckolib/values.rs
+++ b/ports/geckolib/values.rs
@@ -4,10 +4,44 @@
 
 use app_units::Au;
 use cssparser::RGBA;
-use gecko_bindings::structs::{nsStyleUnion, nsStyleUnit};
+use gecko_bindings::structs::{nsStyleCoord, nsStyleUnion, nsStyleUnit};
 use std::cmp::max;
 use style::values::computed::{LengthOrPercentage, LengthOrPercentageOrAuto, LengthOrPercentageOrNone};
 
+pub trait StyleCoordHelpers {
+    fn set<T: ToGeckoStyleCoord>(&mut self, val: T);
+    fn set_auto(&mut self);
+    fn set_coord(&mut self, val: Au);
+    fn set_int(&mut self, val: i32);
+    fn set_percent(&mut self, val: f32);
+}
+
+impl StyleCoordHelpers for nsStyleCoord {
+    fn set<T: ToGeckoStyleCoord>(&mut self, val: T) {
+        val.to_gecko_style_coord(&mut self.mUnit, &mut self.mValue);
+    }
+
+    fn set_auto(&mut self) {
+        self.mUnit = nsStyleUnit::eStyleUnit_Auto;
+        unsafe { *self.mValue.mInt.as_mut() = 0; }
+    }
+
+    fn set_coord(&mut self, val: Au) {
+        self.mUnit = nsStyleUnit::eStyleUnit_Coord;
+        unsafe { *self.mValue.mInt.as_mut() = val.0; }
+    }
+
+    fn set_percent(&mut self, val: f32) {
+        self.mUnit = nsStyleUnit::eStyleUnit_Percent;
+        unsafe { *self.mValue.mFloat.as_mut() = val; }
+    }
+
+    fn set_int(&mut self, val: i32) {
+        self.mUnit = nsStyleUnit::eStyleUnit_Integer;
+        unsafe { *self.mValue.mInt.as_mut() = val; }
+    }
+}
+
 pub trait ToGeckoStyleCoord {
     fn to_gecko_style_coord(&self, unit: &mut nsStyleUnit, union: &mut nsStyleUnion);
 }