--- a/servo/components/style/properties/helpers/animated_properties.mako.rs
+++ b/servo/components/style/properties/helpers/animated_properties.mako.rs
@@ -2155,16 +2155,87 @@ impl Interpolate for IntermediateRGBA {
             let blue = try!((self.blue * self.alpha)
                              .interpolate(&(other.blue * other.alpha), progress))
                              * 1. / alpha;
             Ok(IntermediateRGBA::new(red, green, blue, alpha))
         }
     }
 }
 
+<%def name="impl_intermediate_type_for_shadow(type)">
+    #[derive(Copy, Clone, Debug, PartialEq)]
+    #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+    #[allow(missing_docs)]
+    /// Intermediate type for box-shadow and text-shadow.
+    /// The difference between normal shadow type is that this type uses
+    /// IntermediateColor instead of ParserColor.
+    pub struct Intermediate${type}Shadow {
+        pub offset_x: Au,
+        pub offset_y: Au,
+        pub blur_radius: Au,
+        pub color: IntermediateColor,
+        % if type == "Box":
+        pub spread_radius: Au,
+        pub inset: bool,
+        % endif
+    }
+
+    #[derive(Clone, Debug, PartialEq)]
+    #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+    #[allow(missing_docs)]
+    /// Intermediate type for box-shadow list and text-shadow list.
+    pub struct Intermediate${type}ShadowList(pub Vec<Intermediate${type}Shadow>);
+
+    impl <'a> From<<&'a Intermediate${type}ShadowList> for ${type}ShadowList {
+        fn from(shadow_list: &Intermediate${type}ShadowList) -> ${type}ShadowList {
+            ${type}ShadowList(shadow_list.0.iter().map(|s| s.into()).collect())
+        }
+    }
+
+    impl <'a> From<<&'a ${type}ShadowList> for Intermediate${type}ShadowList {
+        fn from(shadow_list: &${type}ShadowList) -> Intermediate${type}ShadowList {
+            Intermediate${type}ShadowList(shadow_list.0.iter().map(|s| s.into()).collect())
+        }
+    }
+
+    impl <'a> From<<&'a Intermediate${type}Shadow> for ${type}Shadow {
+        fn from(shadow: &Intermediate${type}Shadow) -> ${type}Shadow {
+            ${type}Shadow {
+                offset_x: shadow.offset_x,
+                offset_y: shadow.offset_y,
+                blur_radius: shadow.blur_radius,
+                color: (&shadow.color).into(),
+                % if type == "Box":
+                spread_radius: shadow.spread_radius,
+                inset: shadow.inset,
+                % endif
+            }
+        }
+    }
+
+    impl <'a> From<<&'a ${type}Shadow> for Intermediate${type}Shadow {
+        fn from(shadow: &${type}Shadow) -> Intermediate${type}Shadow {
+            Intermediate${type}Shadow {
+                offset_x: shadow.offset_x,
+                offset_y: shadow.offset_y,
+                blur_radius: shadow.blur_radius,
+                color: (&shadow.color).into(),
+                % if type == "Box":
+                spread_radius: shadow.spread_radius,
+                inset: shadow.inset,
+                % endif
+            }
+        }
+    }
+    ${impl_interpolate_for_shadow('Intermediate%sShadow' % type,
+                                  'IntermediateColor::IntermediateRGBA(IntermediateRGBA::transparent())')}
+</%def>
+
+${impl_intermediate_type_for_shadow('Box')}
+
 impl<'a> From<<&'a Either<CSSParserColor, Auto>> for Either<IntermediateColor, Auto> {
     fn from(from: &Either<CSSParserColor, Auto>) -> Either<IntermediateColor, Auto> {
         match *from {
             Either::First(ref from) =>
                 match *from {
                     CSSParserColor::RGBA(ref color) =>
                         Either::First(IntermediateColor::IntermediateRGBA(
                             IntermediateRGBA::new(color.red_f32(),

--- a/servo/components/style/properties/longhand/effects.mako.rs
+++ b/servo/components/style/properties/longhand/effects.mako.rs
@@ -10,17 +10,18 @@
 ${helpers.predefined_type("opacity",
                           "Opacity",
                           "1.0",
                           animation_value_type="ComputedValue",
                           flags="CREATES_STACKING_CONTEXT",
                           spec="https://drafts.csswg.org/css-color/#opacity")}
 
 <%helpers:vector_longhand name="box-shadow" allow_empty="True"
-                          animation_value_type="ComputedValue" extra_prefixes="webkit"
+                          animation_value_type="IntermediateBoxShadowList"
+                          extra_prefixes="webkit"
                           spec="https://drafts.csswg.org/css-backgrounds/#box-shadow">
     use cssparser;
     use std::fmt;
     use style_traits::ToCss;
     use values::HasViewportPercentage;
 
     pub type SpecifiedValue = specified::Shadow;