diff --git a/components/style/custom_properties.rs b/components/style/custom_properties.rs
index 6d7a198e047..574031453e5 100644
--- a/components/style/custom_properties.rs
+++ b/components/style/custom_properties.rs
@@ -25,6 +25,7 @@ use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
 ///
 /// TODO(emilio): If this becomes a bit more complex we should probably move it
 /// to the `media_queries` module, or something.
+#[derive(Debug, MallocSizeOf)]
 pub struct CssEnvironment;
 
 struct EnvironmentVariable {
diff --git a/components/style/properties/helpers/animated_properties.mako.rs b/components/style/properties/helpers/animated_properties.mako.rs
index 58c727ca416..ba1a6444d42 100644
--- a/components/style/properties/helpers/animated_properties.mako.rs
+++ b/components/style/properties/helpers/animated_properties.mako.rs
@@ -18,7 +18,7 @@ use num_traits::Zero;
 use properties::{CSSWideKeyword, PropertyDeclaration};
 use properties::longhands;
 use properties::longhands::visibility::computed_value::T as Visibility;
-use properties::{LonghandId, ShorthandId};
+use properties::LonghandId;
 use servo_arc::Arc;
 use smallvec::SmallVec;
 use std::{cmp, ptr};
@@ -50,6 +50,7 @@ use void::{self, Void};
 #[allow(non_upper_case_globals)]
 impl From<nsCSSPropertyID> for TransitionProperty {
     fn from(property: nsCSSPropertyID) -> TransitionProperty {
+        use properties::ShorthandId;
         match property {
             % for prop in data.longhands:
             ${prop.nscsspropertyid()} => {
diff --git a/components/style/servo/media_queries.rs b/components/style/servo/media_queries.rs
index 98b1ec7ae6f..bae0aa3978b 100644
--- a/components/style/servo/media_queries.rs
+++ b/components/style/servo/media_queries.rs
@@ -6,6 +6,7 @@
 
 use app_units::Au;
 use cssparser::RGBA;
+use custom_properties::CssEnvironment;
 use euclid::{Size2D, TypedScale, TypedSize2D};
 use media_queries::MediaType;
 use media_queries::media_feature::{AllowsRanges, ParsingRequirements};
@@ -49,6 +50,9 @@ pub struct Device {
     /// Whether any styles computed in the document relied on the viewport size.
     #[ignore_malloc_size_of = "Pure stack type"]
     used_viewport_units: AtomicBool,
+    /// The CssEnvironment object responsible of getting CSS environment
+    /// variables.
+    environment: CssEnvironment,
 }
 
 impl Device {
@@ -66,9 +70,16 @@ impl Device {
             root_font_size: AtomicIsize::new(FontSize::medium().size().0 as isize),
             used_root_font_size: AtomicBool::new(false),
             used_viewport_units: AtomicBool::new(false),
+            environment: CssEnvironment,
         }
     }
 
+    /// Get the relevant environment to resolve `env()` functions.
+    #[inline]
+    pub fn environment(&self) -> &CssEnvironment {
+        &self.environment
+    }
+
     /// Return the default computed values for this device.
     pub fn default_computed_values(&self) -> &ComputedValues {
         // FIXME(bz): This isn't really right, but it's no more wrong
diff --git a/tests/unit/style/custom_properties.rs b/tests/unit/style/custom_properties.rs
index dfb0c825627..aeefe6e19b9 100644
--- a/tests/unit/style/custom_properties.rs
+++ b/tests/unit/style/custom_properties.rs
@@ -4,7 +4,7 @@
 
 use cssparser::{Parser, ParserInput};
 use servo_arc::Arc;
-use style::custom_properties::{Name, SpecifiedValue, CustomPropertiesMap, CustomPropertiesBuilder};
+use style::custom_properties::{Name, SpecifiedValue, CustomPropertiesMap, CustomPropertiesBuilder, CssEnvironment};
 use style::properties::CustomDeclarationValue;
 use test::{self, Bencher};
 
@@ -18,7 +18,8 @@ fn cascade(
         (Name::from(name), SpecifiedValue::parse(&mut parser).unwrap())
     }).collect::<Vec<_>>();
 
-    let mut builder = CustomPropertiesBuilder::new(inherited);
+    let env = CssEnvironment;
+    let mut builder = CustomPropertiesBuilder::new(inherited, &env);
 
     for &(ref name, ref val) in &values {
         builder.cascade(name, &CustomDeclarationValue::Value(val.clone()));