diff --git a/components/style/properties/helpers/animated_properties.mako.rs b/components/style/properties/helpers/animated_properties.mako.rs
index ba1a6444d42..2ab27687241 100644
--- a/components/style/properties/helpers/animated_properties.mako.rs
+++ b/components/style/properties/helpers/animated_properties.mako.rs
@@ -2212,7 +2212,6 @@ impl ComputedScale {
             Scale::None => (1.0, 1.0, 1.0),
             Scale::Scale3D(sx, sy, sz) => (sx, sy, sz),
             Scale::Scale(sx, sy) => (sx, sy, 1.),
-            Scale::ScaleX(sx) => (sx, 1., 1.),
         }
     }
 }
@@ -2224,21 +2223,38 @@ impl Animate for ComputedScale {
         other: &Self,
         procedure: Procedure,
     ) -> Result<Self, ()> {
-        let from = ComputedScale::resolve(self);
-        let to = ComputedScale::resolve(other);
-
-        // FIXME(emilio, bug 1464791): why does this do something different than
-        // Scale3D / TransformOperation::Scale3D?
-        if procedure == Procedure::Add {
-            // scale(x1,y1,z1)*scale(x2,y2,z2) = scale(x1*x2, y1*y2, z1*z2)
-            return Ok(Scale::Scale3D(from.0 * to.0, from.1 * to.1, from.2 * to.2));
+        match (self, other) {
+            (&Scale::None, &Scale::None) => Ok(Scale::None),
+            (&Scale::Scale3D(_, ..), _) | (_, &Scale::Scale3D(_, ..)) => {
+                let from = ComputedScale::resolve(self);
+                let to = ComputedScale::resolve(other);
+                // FIXME(emilio, bug 1464791): why does this do something different than
+                // Scale3D / TransformOperation::Scale3D?
+                if procedure == Procedure::Add {
+                    // scale(x1,y1,z1)*scale(x2,y2,z2) = scale(x1*x2, y1*y2, z1*z2)
+                    return Ok(Scale::Scale3D(from.0 * to.0, from.1 * to.1, from.2 * to.2));
+                }
+                Ok(Scale::Scale3D(
+                    animate_multiplicative_factor(from.0, to.0, procedure)?,
+                    animate_multiplicative_factor(from.1, to.1, procedure)?,
+                    animate_multiplicative_factor(from.2, to.2, procedure)?,
+                ))
+            },
+            (&Scale::Scale(_, ..), _) | (_, &Scale::Scale(_, ..)) => {
+                let from = ComputedScale::resolve(self);
+                let to = ComputedScale::resolve(other);
+                // FIXME(emilio, bug 1464791): why does this do something different than
+                // Scale / TransformOperation::Scale?
+                if procedure == Procedure::Add {
+                    // scale(x1,y1)*scale(x2,y2) = scale(x1*x2, y1*y2)
+                    return Ok(Scale::Scale(from.0 * to.0, from.1 * to.1));
+                }
+                Ok(Scale::Scale(
+                    animate_multiplicative_factor(from.0, to.0, procedure)?,
+                    animate_multiplicative_factor(from.1, to.1, procedure)?,
+                ))
+            },
         }
-
-        Ok(Scale::Scale3D(
-            animate_multiplicative_factor(from.0, to.0, procedure)?,
-            animate_multiplicative_factor(from.1, to.1, procedure)?,
-            animate_multiplicative_factor(from.2, to.2, procedure)?,
-        ))
     }
 }
 
diff --git a/components/style/values/computed/transform.rs b/components/style/values/computed/transform.rs
index 9590ad4025f..6b781c7bc54 100644
--- a/components/style/values/computed/transform.rs
+++ b/components/style/values/computed/transform.rs
@@ -367,8 +367,9 @@ impl Scale {
     pub fn to_transform_operation(&self) -> Option<TransformOperation> {
         match *self {
             generic::Scale::None => None,
-            generic::Scale::ScaleX(sx) => Some(generic::TransformOperation::ScaleX(sx)),
-            generic::Scale::Scale(sx, sy) => Some(generic::TransformOperation::Scale(sx, Some(sy))),
+            generic::Scale::Scale(sx, sy) => {
+                Some(generic::TransformOperation::Scale(sx, Some(sy)))
+            },
             generic::Scale::Scale3D(sx, sy, sz) => {
                 Some(generic::TransformOperation::Scale3D(sx, sy, sz))
             },
@@ -378,8 +379,8 @@ impl Scale {
     /// Convert Scale to TransformOperation.
     pub fn from_transform_operation(operation: &TransformOperation) -> Scale {
         match *operation {
-            generic::TransformOperation::ScaleX(sx) => generic::Scale::ScaleX(sx),
             generic::TransformOperation::Scale(sx, Some(sy)) => generic::Scale::Scale(sx, sy),
+            generic::TransformOperation::Scale(sx, None) => generic::Scale::Scale(sx, sx),
             generic::TransformOperation::Scale3D(sx, sy, sz) => generic::Scale::Scale3D(sx, sy, sz),
             _ => unreachable!("Found unexpected value for scale"),
         }
diff --git a/components/style/values/generics/transform.rs b/components/style/values/generics/transform.rs
index b4d011fd682..5ace667ec6e 100644
--- a/components/style/values/generics/transform.rs
+++ b/components/style/values/generics/transform.rs
@@ -7,6 +7,8 @@
 use app_units::Au;
 use euclid::{self, Rect, Transform3D};
 use num_traits::Zero;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
 use values::computed::length::Length as ComputedLength;
 use values::computed::length::LengthOrPercentage as ComputedLengthOrPercentage;
 use values::specified::angle::Angle as SpecifiedAngle;
@@ -560,7 +562,6 @@ pub enum Rotate<Number, Angle> {
     SpecifiedValueInfo,
     ToAnimatedZero,
     ToComputedValue,
-    ToCss,
 )]
 /// A value of the `Scale` property
 ///
@@ -568,14 +569,38 @@ pub enum Rotate<Number, Angle> {
 pub enum Scale<Number> {
     /// 'none'
     None,
-    /// '<number>'
-    ScaleX(Number),
-    /// '<number>{2}'
+    /// '<number>{1,2}'
     Scale(Number, Number),
     /// '<number>{3}'
     Scale3D(Number, Number, Number),
 }
 
+impl<Number: ToCss + PartialEq> ToCss for Scale<Number> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        match self {
+            &Scale::None => dest.write_str("none"),
+            &Scale::Scale(ref x, ref y) => {
+                x.to_css(dest)?;
+                if x != y {
+                    dest.write_char(' ')?;
+                    y.to_css(dest)?;
+                }
+                Ok(())
+            },
+            &Scale::Scale3D(ref x, ref y, ref z) => {
+                x.to_css(dest)?;
+                dest.write_char(' ')?;
+                y.to_css(dest)?;
+                dest.write_char(' ')?;
+                z.to_css(dest)
+            },
+        }
+    }
+}
+
 #[derive(
     Clone,
     ComputeSquaredDistance,
diff --git a/components/style/values/specified/transform.rs b/components/style/values/specified/transform.rs
index d306211329e..d397d3d3607 100644
--- a/components/style/values/specified/transform.rs
+++ b/components/style/values/specified/transform.rs
@@ -423,6 +423,6 @@ impl Parse for Scale {
         }
 
         // 'scale: <number>'
-        Ok(generic::Scale::ScaleX(sx))
+        Ok(generic::Scale::Scale(sx, sx))
     }
 }