diff --git a/components/script/dom/csskeyframesrule.rs b/components/script/dom/csskeyframesrule.rs
index bda3ee2ea20..41d7beeaf80 100644
--- a/components/script/dom/csskeyframesrule.rs
+++ b/components/script/dom/csskeyframesrule.rs
@@ -19,7 +19,7 @@ use parking_lot::RwLock;
 use std::sync::Arc;
 use style::keyframes::{Keyframe, KeyframeSelector};
 use style::parser::ParserContextExtraData;
-use style::stylesheets::{KeyframesRule, Origin};
+use style::stylesheets::KeyframesRule;
 use style_traits::ToCss;
 
 #[dom_struct]
@@ -83,8 +83,7 @@ impl CSSKeyframesRuleMethods for CSSKeyframesRule {
     fn AppendRule(&self, rule: DOMString) {
         let global = self.global();
         let window = global.as_window();
-        let doc = window.Document();
-        let rule = Keyframe::parse(&rule, Origin::Author, doc.url().clone(),
+        let rule = Keyframe::parse(&rule, self.cssrule.parent_stylesheet().style_stylesheet(),
                                    ParserContextExtraData::default());
         if let Ok(rule) = rule {
             self.keyframesrule.write().keyframes.push(rule);
diff --git a/components/script/dom/cssrulelist.rs b/components/script/dom/cssrulelist.rs
index 643cce9a944..e51ae3c78be 100644
--- a/components/script/dom/cssrulelist.rs
+++ b/components/script/dom/cssrulelist.rs
@@ -84,10 +84,10 @@ impl CSSRuleList {
 
         let global = self.global();
         let window = global.as_window();
-        let doc = window.Document();
         let index = idx as usize;
 
-        let new_rule = css_rules.insert_rule(rule, doc.url().clone(), index, nested)?;
+        let parent_stylesheet = self.parent_stylesheet.style_stylesheet();
+        let new_rule = css_rules.insert_rule(rule, parent_stylesheet, index, nested)?;
 
         let parent_stylesheet = &*self.parent_stylesheet;
         let dom_rule = CSSRule::new_specific(&window, parent_stylesheet, new_rule);
diff --git a/components/script/dom/cssstylesheet.rs b/components/script/dom/cssstylesheet.rs
index 2e643f3e8a2..93aefa8f852 100644
--- a/components/script/dom/cssstylesheet.rs
+++ b/components/script/dom/cssstylesheet.rs
@@ -67,6 +67,10 @@ impl CSSStyleSheet {
             self.global().as_window().Document().invalidate_stylesheets();
         }
     }
+
+    pub fn style_stylesheet(&self) -> &StyleStyleSheet {
+        &self.style_stylesheet
+    }
 }
 
 impl CSSStyleSheetMethods for CSSStyleSheet {
diff --git a/components/style/keyframes.rs b/components/style/keyframes.rs
index 7c9b969a210..831627d42c3 100644
--- a/components/style/keyframes.rs
+++ b/components/style/keyframes.rs
@@ -9,11 +9,10 @@ use parser::{ParserContext, ParserContextExtraData, log_css_error};
 use properties::{Importance, PropertyDeclaration, PropertyDeclarationBlock};
 use properties::PropertyDeclarationParseResult;
 use properties::animated_properties::TransitionProperty;
-use servo_url::ServoUrl;
 use std::fmt;
 use std::sync::Arc;
 use style_traits::ToCss;
-use stylesheets::{MemoryHoleReporter, Origin};
+use stylesheets::{MemoryHoleReporter, Stylesheet};
 
 /// A number from 1 to 100, indicating the percentage of the animation where
 /// this keyframe should run.
@@ -108,11 +107,11 @@ impl ToCss for Keyframe {
 
 
 impl Keyframe {
-    pub fn parse(css: &str, origin: Origin,
-                 base_url: ServoUrl,
-                 extra_data: ParserContextExtraData) -> Result<Arc<RwLock<Self>>, ()> {
+    pub fn parse(css: &str, parent_stylesheet: &Stylesheet, extra_data: ParserContextExtraData)
+                 -> Result<Arc<RwLock<Self>>, ()> {
         let error_reporter = Box::new(MemoryHoleReporter);
-        let context = ParserContext::new_with_extra_data(origin, &base_url,
+        let context = ParserContext::new_with_extra_data(parent_stylesheet.origin,
+                                                         &parent_stylesheet.base_url,
                                                          error_reporter,
                                                          extra_data);
         let mut input = Parser::new(css);
diff --git a/components/style/stylesheets.rs b/components/style/stylesheets.rs
index 1529a2e77ef..f05cd4a7df6 100644
--- a/components/style/stylesheets.rs
+++ b/components/style/stylesheets.rs
@@ -88,7 +88,7 @@ impl CssRules {
     }
 
     // https://drafts.csswg.org/cssom/#insert-a-css-rule
-    pub fn insert_rule(&self, rule: &str, base_url: ServoUrl, index: usize, nested: bool)
+    pub fn insert_rule(&self, rule: &str, parent_stylesheet: &Stylesheet, index: usize, nested: bool)
                        -> Result<CssRule, RulesMutateError> {
         let mut rules = self.0.write();
 
@@ -108,7 +108,7 @@ impl CssRules {
 
         // Step 3, 4
         // XXXManishearth should we also store the namespace map?
-        let (new_rule, new_state) = try!(CssRule::parse(&rule, Origin::Author, base_url,
+        let (new_rule, new_state) = try!(CssRule::parse(&rule, parent_stylesheet,
                                                         ParserContextExtraData::default(), state));
 
         // Step 5
@@ -282,13 +282,15 @@ impl CssRule {
 
     // input state is None for a nested rule
     // Returns a parsed CSS rule and the final state of the parser
-    pub fn parse(css: &str, origin: Origin,
-                    base_url: ServoUrl,
-                    extra_data: ParserContextExtraData,
-                    state: Option<State>) -> Result<(Self, State), SingleRuleParseError> {
+    pub fn parse(css: &str,
+                 parent_stylesheet: &Stylesheet,
+                 extra_data: ParserContextExtraData,
+                 state: Option<State>)
+                 -> Result<(Self, State), SingleRuleParseError> {
         let error_reporter = Box::new(MemoryHoleReporter);
-        let mut namespaces = Namespaces::default();
-        let context = ParserContext::new_with_extra_data(origin, &base_url,
+        let mut namespaces = parent_stylesheet.namespaces.write();
+        let context = ParserContext::new_with_extra_data(parent_stylesheet.origin,
+                                                         &parent_stylesheet.base_url,
                                                          error_reporter.clone(),
                                                          extra_data);
         let mut input = Parser::new(css);
@@ -296,7 +298,7 @@ impl CssRule {
         // nested rules are in the body state
         let state = state.unwrap_or(State::Body);
         let mut rule_parser = TopLevelRuleParser {
-            stylesheet_origin: origin,
+            stylesheet_origin: parent_stylesheet.origin,
             context: context,
             state: Cell::new(state),
             namespaces: &mut namespaces,