diff --git a/components/style/values/computed/background.rs b/components/style/values/computed/background.rs
index 82b6ba74f28..f3180c54ebe 100644
--- a/components/style/values/computed/background.rs
+++ b/components/style/values/computed/background.rs
@@ -6,7 +6,7 @@
 
 use properties::animated_properties::RepeatableListAnimatable;
 use properties::longhands::background_size::computed_value::T as BackgroundSizeList;
-use values::animated::{Animate, Procedure, ToAnimatedValue, ToAnimatedZero};
+use values::animated::{ToAnimatedValue, ToAnimatedZero};
 use values::computed::length::LengthOrPercentageOrAuto;
 use values::generics::background::BackgroundSize as GenericBackgroundSize;
 
@@ -15,23 +15,6 @@ pub type BackgroundSize = GenericBackgroundSize<LengthOrPercentageOrAuto>;
 
 impl RepeatableListAnimatable for BackgroundSize {}
 
-impl Animate for BackgroundSize {
-    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
-        match (self, other) {
-            (
-                &GenericBackgroundSize::Explicit { width: self_width, height: self_height },
-                &GenericBackgroundSize::Explicit { width: other_width, height: other_height },
-            ) => {
-                Ok(GenericBackgroundSize::Explicit {
-                    width: self_width.animate(&other_width, procedure)?,
-                    height: self_height.animate(&other_height, procedure)?,
-                })
-            }
-            _ => Err(()),
-        }
-    }
-}
-
 impl ToAnimatedZero for BackgroundSize {
     #[inline]
     fn to_animated_zero(&self) -> Result<Self, ()> { Err(()) }
diff --git a/components/style/values/generics/background.rs b/components/style/values/generics/background.rs
index 8a79691f3b9..abcfb655eec 100644
--- a/components/style/values/generics/background.rs
+++ b/components/style/values/generics/background.rs
@@ -5,8 +5,9 @@
 //! Generic types for CSS values related to backgrounds.
 
 /// A generic value for the `background-size` property.
-#[derive(Clone, ComputeSquaredDistance, Copy, Debug, HasViewportPercentage, PartialEq, ToComputedValue, ToCss)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[derive(Animate, Clone, ComputeSquaredDistance, Copy, Debug)]
+#[derive(HasViewportPercentage, PartialEq, ToComputedValue, ToCss)]
 pub enum BackgroundSize<LengthOrPercentageOrAuto> {
     /// `<width> <height>`
     Explicit {
@@ -16,8 +17,10 @@ pub enum BackgroundSize<LengthOrPercentageOrAuto> {
         height: LengthOrPercentageOrAuto
     },
     /// `cover`
+    #[animation(error)]
     Cover,
     /// `contain`
+    #[animation(error)]
     Contain,
 }