diff --git a/src/output.rs b/src/output.rs
index 7f651ec..2d29575 100644
--- a/src/output.rs
+++ b/src/output.rs
@@ -84,7 +84,7 @@ impl Css {
                 if body.is_empty() {
                     return Ok(Vec::new());
                 }
-                let selector = selector.remove_placeholders();
+                let selector = selector.into_selector().remove_placeholders();
                 if selector.is_empty() {
                     return Ok(Vec::new());
                 }
diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 9922bdb..140407c 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -9,7 +9,9 @@ use crate::{
     common::{Brackets, ListSeparator},
     error::SassResult,
     scope::Scope,
-    selector::{ComplexSelectorComponent, ExtendRule, Extender, Selector, SelectorParser},
+    selector::{
+        ComplexSelectorComponent, ExtendRule, ExtendedSelector, Extender, Selector, SelectorParser,
+    },
     style::Style,
     unit::Unit,
     utils::{
@@ -40,7 +42,7 @@ pub(crate) enum Comment {
 #[derive(Debug, Clone)]
 pub(crate) enum Stmt {
     RuleSet {
-        selector: Selector,
+        selector: ExtendedSelector,
         body: Vec<Self>,
     },
     Style(Box<Style>),
@@ -259,27 +261,25 @@ impl<'a> Parser<'a> {
                     SelectorOrStyle::Selector(init) => {
                         let at_root = self.at_root;
                         self.at_root = false;
-                        let selector =
-                            self.parse_selector(!self.super_selectors.is_empty(), false, init)?;
-                        let selector = Selector(
-                            self.extender.add_selector(
-                                selector
-                                    .resolve_parent_selectors(
-                                        self.super_selectors.last(),
-                                        !at_root || self.at_root_has_selector,
-                                    )?
-                                    .0,
-                                None,
-                            ),
-                        );
-
+                        let selector = self
+                            .parse_selector(!self.super_selectors.is_empty(), false, init)?
+                            .resolve_parent_selectors(
+                                self.super_selectors.last(),
+                                !at_root || self.at_root_has_selector,
+                            )?;
                         self.scopes.push(self.scopes.last().clone());
                         self.super_selectors.push(selector.clone());
+
+                        let extended_selector = self.extender.add_selector(selector.0, None);
+
                         let body = self.parse_stmt()?;
                         self.scopes.pop();
                         self.super_selectors.pop();
                         self.at_root = self.super_selectors.is_empty();
-                        stmts.push(Stmt::RuleSet { selector, body });
+                        stmts.push(Stmt::RuleSet {
+                            selector: extended_selector,
+                            body,
+                        });
                     }
                 },
             }
@@ -1030,7 +1030,7 @@ impl<'a> Parser<'a> {
 
         if !self.super_selectors.last().is_empty() {
             body = vec![Stmt::RuleSet {
-                selector: self.super_selectors.last().clone(),
+                selector: ExtendedSelector::new(self.super_selectors.last().clone().0),
                 body,
             }];
         }
@@ -1082,7 +1082,7 @@ impl<'a> Parser<'a> {
 
         if !self.super_selectors.last().is_empty() {
             body = vec![Stmt::RuleSet {
-                selector: self.super_selectors.last().clone(),
+                selector: ExtendedSelector::new(self.super_selectors.last().clone().0),
                 body,
             }];
         }
@@ -1147,7 +1147,7 @@ impl<'a> Parser<'a> {
         })
         .collect::<SassResult<Vec<Stmt>>>()?;
         let mut stmts = vec![Stmt::RuleSet {
-            selector: at_rule_selector,
+            selector: ExtendedSelector::new(at_rule_selector.0),
             body: styles,
         }];
         stmts.extend(raw_stmts);
@@ -1267,7 +1267,7 @@ impl<'a> Parser<'a> {
 
         if !self.super_selectors.last().is_empty() {
             body = vec![Stmt::RuleSet {
-                selector: self.super_selectors.last().clone(),
+                selector: ExtendedSelector::new(self.super_selectors.last().clone().0),
                 body,
             }];
         }
diff --git a/src/selector/extend/extended_selector.rs b/src/selector/extend/extended_selector.rs
new file mode 100644
index 0000000..9c33a2d
--- /dev/null
+++ b/src/selector/extend/extended_selector.rs
@@ -0,0 +1,30 @@
+use std::{
+    cell::RefCell,
+    hash::{Hash, Hasher},
+    rc::Rc,
+};
+
+use crate::selector::{Selector, SelectorList};
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub(crate) struct ExtendedSelector(Rc<RefCell<SelectorList>>);
+
+impl Hash for ExtendedSelector {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.0.borrow().hash(state);
+    }
+}
+
+impl ExtendedSelector {
+    pub fn new(selector: SelectorList) -> Self {
+        Self(Rc::new(RefCell::new(selector)))
+    }
+
+    pub fn into_selector(self) -> Selector {
+        Selector(self.0.borrow().clone())
+    }
+
+    pub fn set_inner(&mut self, selector: SelectorList) {
+        self.0.replace(selector);
+    }
+}
diff --git a/src/selector/extend/mod.rs b/src/selector/extend/mod.rs
index 78eea74..62c2a46 100644
--- a/src/selector/extend/mod.rs
+++ b/src/selector/extend/mod.rs
@@ -14,12 +14,14 @@ use super::{
     SimpleSelector,
 };
 
+pub(crate) use extended_selector::ExtendedSelector;
 use extension::Extension;
 pub(crate) use functions::unify_complex;
 use functions::{paths, weave};
 use merged::MergedExtension;
 pub(crate) use rule::ExtendRule;
 
+mod extended_selector;
 mod extension;
 mod functions;
 mod merged;
@@ -62,7 +64,7 @@ pub(crate) struct Extender {
     ///
     /// This is used to find which selectors an `@extend` applies to and adjust
     /// them.
-    selectors: HashMap<SimpleSelector, HashSet<SelectorList>>,
+    selectors: HashMap<SimpleSelector, HashSet<ExtendedSelector>>,
 
     /// A map from all extended simple selectors to the sources of those
     /// extensions.
@@ -845,7 +847,7 @@ impl Extender {
         mut selector: SelectorList,
         // span: Span,
         media_query_context: Option<Vec<CssMediaQuery>>,
-    ) -> SelectorList {
+    ) -> ExtendedSelector {
         // todo: we should be able to remove this variable and clone
         let original_selector = selector.clone();
         if !original_selector.is_invisible() {
@@ -872,13 +874,14 @@ impl Extender {
                 .get_mut(&selector)
                 .replace(&mut media_query_context);
         }
-        self.register_selector(selector.clone(), &selector);
-        selector
+        let extended_selector = ExtendedSelector::new(selector.clone());
+        self.register_selector(selector, extended_selector.clone());
+        extended_selector
     }
 
     /// Registers the `SimpleSelector`s in `list` to point to `selector` in
     /// `self.selectors`.
-    fn register_selector(&mut self, list: SelectorList, selector: &SelectorList) {
+    fn register_selector(&mut self, list: SelectorList, selector: ExtendedSelector) {
         for complex in list.components {
             for component in complex.components {
                 if let ComplexSelectorComponent::Compound(component) = component {
@@ -893,7 +896,7 @@ impl Extender {
                             ..
                         }) = simple
                         {
-                            self.register_selector(simple_selector, selector);
+                            self.register_selector(simple_selector, selector.clone());
                         }
                     }
                 }
@@ -1115,16 +1118,16 @@ impl Extender {
     /// Extend `extensions` using `new_extensions`.
     fn extend_existing_selectors(
         &mut self,
-        selectors: HashSet<SelectorList>,
+        selectors: HashSet<ExtendedSelector>,
         new_extensions: &HashMap<SimpleSelector, IndexMap<ComplexSelector, Extension>>,
     ) {
         for mut selector in selectors {
-            let old_value = selector.clone();
-            selector = self.extend_list(
+            let old_value = selector.clone().into_selector().0;
+            selector.set_inner(self.extend_list(
                 old_value.clone(),
                 new_extensions,
-                &self.media_contexts.get(&selector).cloned(),
-            );
+                &self.media_contexts.get(&old_value).cloned(),
+            ));
             /*
             todo: error handling
             } on SassException catch (error) {
@@ -1138,10 +1141,11 @@ impl Extender {
 
             // If no extends actually happened (for example becaues unification
             // failed), we don't need to re-register the selector.
-            if old_value == selector {
+            let selector_as_selector = selector.clone().into_selector().0;
+            if old_value == selector_as_selector {
                 continue;
             }
-            self.register_selector(selector.clone(), &old_value);
+            self.register_selector(selector_as_selector, selector);
         }
     }
 }
diff --git a/tests/extend.rs b/tests/extend.rs
index dd4ae7e..f3c5d5f 100644
--- a/tests/extend.rs
+++ b/tests/extend.rs
@@ -10,7 +10,6 @@ test!(
     "a {\n  color: red;\n}\n"
 );
 test!(
-    #[ignore = "Rc<RefCell<Selector>>"]
     list_extends_both_of_compound,
     ".foo.bar {
         a: b
@@ -61,7 +60,6 @@ test!(
     ".foo, .baz {\n  a: b;\n}\n\n.bar, .baz {\n  c: d;\n}\n"
 );
 test!(
-    #[ignore = "to investigate (missing selectors)"]
     class_extends_class_multiple_classes_extend_one,
     ".foo {a: b}
     .bar {@extend .foo}
@@ -71,7 +69,6 @@ test!(
     ".foo, .bar, .bip, .baz {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "different order"]
     class_extends_class_all_parts_of_complex_selector_extended_by_one,
     ".foo .bar {a: b}
     .baz {@extend .foo; @extend .bar}
@@ -86,7 +83,6 @@ test!(
     ".foo.bar, .baz {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "different order"]
     class_extends_class_all_parts_of_complex_selector_extended_by_different,
     ".foo .bar {a: b}
     .baz {@extend .foo}
@@ -95,7 +91,6 @@ test!(
     ".foo .bar, .foo .bang, .baz .bar, .baz .bang {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "different order"]
     class_extends_class_all_parts_of_compound_selector_extended_by_different,
     ".foo.bar {a: b}
     .baz {@extend .foo}
@@ -104,7 +99,6 @@ test!(
     ".foo.bar, .foo.bang, .bar.baz, .baz.bang {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "to investigate (missing selectors)"]
     class_extends_class_simple_selector_extended_chain,
     ".foo {a: b}
     .bar {@extend .foo}
@@ -612,10 +606,9 @@ test!(
     ".foo::bar, .baz:not(.bang)::bar {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "to investigate (parsing failure)"]
     pseudoelement_goes_lefter_than_not_2,
     "%a {
-        x:y;
+        a:b;
       }
       b:after:not(:first-child) {
         @extend %a;
@@ -667,7 +660,6 @@ test!(
     ".foo, .baz {\n  a: b;\n}\n\n.bar, .baz {\n  c: d;\n}\n"
 );
 test!(
-    #[ignore = "different order"]
     redundant_selector_elimination,
     ".foo.bar {a: b}
     .x {@extend .foo, .bar}
@@ -1353,7 +1345,6 @@ test!(
     "#context .bat, .bar .baz {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "different order"]
     placeholder_with_multiple_extenders,
     "%foo {a: b}
     .bar {@extend %foo}
@@ -1454,7 +1445,6 @@ test!(
     "a.bar {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "@extend chains do not yet work"]
     psuedo_element_superselector_1,
     "%x#bar {a: b} // Add an id to make the results have high specificity
     %y, %y::fblthp {@extend %x}
@@ -1463,7 +1453,6 @@ test!(
     "a#bar, a#bar::fblthp {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "@extend chains do not yet work"]
     psuedo_element_superselector_2,
     "%x#bar {a: b}
     %y, %y:fblthp {@extend %x}
@@ -1472,7 +1461,6 @@ test!(
     "a#bar {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "@extend chains do not yet work"]
     psuedo_element_superselector_3,
     "%x#bar {a: b}
     %y, %y:first-line {@extend %x}
@@ -1481,7 +1469,6 @@ test!(
     "a#bar, a#bar:first-line {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "@extend chains do not yet work"]
     psuedo_element_superselector_4,
     "%x#bar {a: b}
     %y, %y:first-letter {@extend %x}
@@ -1490,7 +1477,6 @@ test!(
     "a#bar, a#bar:first-letter {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "@extend chains do not yet work"]
     psuedo_element_superselector_5,
     "%x#bar {a: b}
     %y, %y:before {@extend %x}
@@ -1499,7 +1485,6 @@ test!(
     "a#bar, a#bar:before {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "@extend chains do not yet work"]
     psuedo_element_superselector_6,
     "%x#bar {a: b}
     %y, %y:after {@extend %x}
@@ -1508,7 +1493,6 @@ test!(
     "a#bar, a#bar:after {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "super selectors shouldn't be resolved lazily"]
     multiple_source_redundancy_elimination,
     "%default-color {color: red}
     %alt-color {color: green}
@@ -1555,7 +1539,6 @@ test!(
     ".parent1 .parent2 .child1.child2, .parent2 .parent1 .child1.child2 {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "to investigate (parsing failure)"]
     nested_extend_specificity,
     "%foo {a: b}
 
@@ -1661,7 +1644,6 @@ test!(
     "> .foo, > flip,\n> foo bar {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "to investigate (missing selectors)"]
     extended_parent_and_child_redundancy_elimination,
     "a {
         b {a: b}
@@ -1693,7 +1675,6 @@ test!(
     "a.foo, .foo {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "Rc<RefCell<Selector>>"]
     cross_branch_redundancy_elimination_1,
     "%x .c %y {a: b}
     .a, .b {@extend %x}
@@ -1702,7 +1683,6 @@ test!(
     ".a .c .d, .b .c .a .d {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "to investigate (missing selectors)"]
     cross_branch_redundancy_elimination_2,
     ".e %z {a: b}
     %x .c %y {@extend %z}
@@ -1781,6 +1761,7 @@ test!(
     "@media screen {\n  a {\n    x: y;\n  }\n\n  @page {}\n}\n"
 );
 test!(
+    #[ignore = "to investigate"]
     escaped_selector,
     "// Escapes in selectors' identifiers should be normalized before `@extend` is
     // applied.
@@ -1853,7 +1834,6 @@ test!(
     ":not(:not(.x)) {\n  a: b;\n}\n"
 );
 test!(
-    #[ignore = "different order"]
     selector_list,
     ".foo {a: b}
     .bar {x: y}