diff --git a/components/script/dom/htmlmetaelement.rs b/components/script/dom/htmlmetaelement.rs
index fa2fe7846c15..4a59d2f58123 100644
--- a/components/script/dom/htmlmetaelement.rs
+++ b/components/script/dom/htmlmetaelement.rs
@@ -100,6 +100,8 @@ impl HTMLMetaElement {
                     *self.stylesheet.borrow_mut() = Some(Arc::new(Stylesheet {
                         rules: vec![CssRule::Viewport(Arc::new(RwLock::new(translated_rule)))].into(),
                         origin: Origin::Author,
+                        base_url: window_from_node(self).get_url(),
+                        namespaces: Default::default(),
                         media: Default::default(),
                         // Viewport constraints are always recomputed on resize; they don't need to
                         // force all styles to be recomputed.
diff --git a/components/style/stylesheets.rs b/components/style/stylesheets.rs
index 5756504e63b2..1529a2e77ef8 100644
--- a/components/style/stylesheets.rs
+++ b/components/style/stylesheets.rs
@@ -44,7 +44,7 @@ pub enum Origin {
     User,
 }
 
-#[derive(Default)]
+#[derive(Default, Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct Namespaces {
     pub default: Option<Namespace>,
@@ -166,6 +166,8 @@ pub struct Stylesheet {
     /// List of media associated with the Stylesheet.
     pub media: Arc<RwLock<MediaList>>,
     pub origin: Origin,
+    pub base_url: ServoUrl,
+    pub namespaces: RwLock<Namespaces>,
     pub dirty_on_viewport_size_change: AtomicBool,
     pub disabled: AtomicBool,
 }
@@ -435,37 +437,40 @@ impl Stylesheet {
                     error_reporter: Box<ParseErrorReporter + Send>,
                     extra_data: ParserContextExtraData) -> Stylesheet {
         let mut namespaces = Namespaces::default();
-        let rule_parser = TopLevelRuleParser {
-            stylesheet_origin: origin,
-            namespaces: &mut namespaces,
-            context: ParserContext::new_with_extra_data(origin, &base_url, error_reporter.clone(),
-                                                        extra_data),
-            state: Cell::new(State::Start),
-        };
-        let mut input = Parser::new(css);
-        input.look_for_viewport_percentages();
-
         let mut rules = vec![];
+        let dirty_on_viewport_size_change;
         {
-            let mut iter = RuleListParser::new_for_stylesheet(&mut input, rule_parser);
-            while let Some(result) = iter.next() {
-                match result {
-                    Ok(rule) => rules.push(rule),
-                    Err(range) => {
-                        let pos = range.start;
-                        let message = format!("Invalid rule: '{}'", iter.input.slice(range));
-                        let context = ParserContext::new(origin, &base_url, error_reporter.clone());
-                        log_css_error(iter.input, pos, &*message, &context);
+            let rule_parser = TopLevelRuleParser {
+                stylesheet_origin: origin,
+                namespaces: &mut namespaces,
+                context: ParserContext::new_with_extra_data(origin, &base_url, error_reporter, extra_data),
+                state: Cell::new(State::Start),
+            };
+            let mut input = Parser::new(css);
+            input.look_for_viewport_percentages();
+            {
+                let mut iter = RuleListParser::new_for_stylesheet(&mut input, rule_parser);
+                while let Some(result) = iter.next() {
+                    match result {
+                        Ok(rule) => rules.push(rule),
+                        Err(range) => {
+                            let pos = range.start;
+                            let message = format!("Invalid rule: '{}'", iter.input.slice(range));
+                            log_css_error(iter.input, pos, &*message, &iter.parser.context);
+                        }
                     }
                 }
             }
+            dirty_on_viewport_size_change = input.seen_viewport_percentages();
         }
 
         Stylesheet {
             origin: origin,
+            base_url: base_url,
+            namespaces: RwLock::new(namespaces),
             rules: rules.into(),
             media: Arc::new(RwLock::new(media)),
-            dirty_on_viewport_size_change: AtomicBool::new(input.seen_viewport_percentages()),
+            dirty_on_viewport_size_change: AtomicBool::new(dirty_on_viewport_size_change),
             disabled: AtomicBool::new(false),
         }
     }
diff --git a/tests/unit/style/stylesheets.rs b/tests/unit/style/stylesheets.rs
index 629bef96d282..1d7fb34fc988 100644
--- a/tests/unit/style/stylesheets.rs
+++ b/tests/unit/style/stylesheets.rs
@@ -19,7 +19,8 @@ use style::parser::ParserContextExtraData;
 use style::properties::{PropertyDeclaration, PropertyDeclarationBlock, DeclaredValue, longhands};
 use style::properties::Importance;
 use style::properties::longhands::animation_play_state;
-use style::stylesheets::{Stylesheet, NamespaceRule, CssRule, StyleRule, KeyframesRule, Origin};
+use style::stylesheets::{Origin, Namespaces};
+use style::stylesheets::{Stylesheet, NamespaceRule, CssRule, StyleRule, KeyframesRule};
 use style::values::specified::{LengthOrPercentageOrAuto, Percentage};
 
 #[test]
@@ -50,12 +51,16 @@ fn test_parse_stylesheet() {
             }
         }";
     let url = ServoUrl::parse("about::test").unwrap();
-    let stylesheet = Stylesheet::from_str(css, url, Origin::UserAgent, Default::default(),
+    let stylesheet = Stylesheet::from_str(css, url.clone(), Origin::UserAgent, Default::default(),
                                           Box::new(CSSErrorReporterTest),
                                           ParserContextExtraData::default());
+    let mut namespaces = Namespaces::default();
+    namespaces.default = Some(ns!(html));
     let expected = Stylesheet {
         origin: Origin::UserAgent,
         media: Default::default(),
+        namespaces: RwLock::new(namespaces),
+        base_url: url,
         dirty_on_viewport_size_change: AtomicBool::new(false),
         disabled: AtomicBool::new(false),
         rules: vec![