diff --git a/components/malloc_size_of/lib.rs b/components/malloc_size_of/lib.rs
index 3801669ab5d..5e97a2709dc 100644
--- a/components/malloc_size_of/lib.rs
+++ b/components/malloc_size_of/lib.rs
@@ -58,9 +58,9 @@ extern crate smallvec;
 extern crate string_cache;
 #[cfg(feature = "url")]
 extern crate url;
+extern crate void;
 #[cfg(feature = "webrender_api")]
 extern crate webrender_api;
-extern crate void;
 #[cfg(feature = "servo")]
 extern crate xml5ever;
 
diff --git a/components/style/properties/helpers/animated_properties.mako.rs b/components/style/properties/helpers/animated_properties.mako.rs
index 703b6be9fe5..a5f1abd935e 100644
--- a/components/style/properties/helpers/animated_properties.mako.rs
+++ b/components/style/properties/helpers/animated_properties.mako.rs
@@ -364,7 +364,8 @@ pub enum AnimationValue {
 impl AnimationValue {
     /// Returns the longhand id this animated value corresponds to.
     pub fn id(&self) -> LonghandId {
-        match *self {
+        let id = unsafe { *(self as *const _ as *const LonghandId) };
+        debug_assert_eq!(id, match *self {
             % for prop in data.longhands:
             % if prop.animatable:
             AnimationValue::${prop.camel_case}(..) => LonghandId::${prop.camel_case},
@@ -372,7 +373,8 @@ impl AnimationValue {
             AnimationValue::${prop.camel_case}(void) => void::unreachable(void),
             % endif
             % endfor
-        }
+        });
+        id
     }
 
     /// "Uncompute" this animation value in order to be used inside the CSS