diff --git a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp
index 36dc0b9df8..7ec8a5248e 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp
+++ b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp
@@ -6,6 +6,8 @@
 
 #include <LibWeb/CSS/CSSStyleSheet.h>
 #include <LibWeb/CSS/Parser/Parser.h>
+#include <LibWeb/CSS/StyleSheetList.h>
+#include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/ExceptionOr.h>
 
 namespace Web::CSS {
@@ -36,7 +38,16 @@ DOM::ExceptionOr<unsigned> CSSStyleSheet::insert_rule(StringView rule, unsigned
     // FIXME: 5. If parsed rule is an @import rule, and the constructed flag is set, throw a SyntaxError DOMException.
 
     // 6. Return the result of invoking insert a CSS rule rule in the CSS rules at index.
-    return m_rules->insert_a_css_rule(parsed_rule.release_nonnull(), index);
+    auto result = m_rules->insert_a_css_rule(parsed_rule.release_nonnull(), index);
+
+    if (!result.is_exception()) {
+        if (m_style_sheet_list) {
+            m_style_sheet_list->bump_generation();
+            m_style_sheet_list->document().invalidate_style();
+        }
+    }
+
+    return result;
 }
 
 // https://www.w3.org/TR/cssom/#dom-cssstylesheet-deleterule
@@ -47,7 +58,14 @@ DOM::ExceptionOr<void> CSSStyleSheet::delete_rule(unsigned index)
     // FIXME: 2. If the disallow modification flag is set, throw a NotAllowedError DOMException.
 
     // 3. Remove a CSS rule in the CSS rules at index.
-    return m_rules->remove_a_css_rule(index);
+    auto result = m_rules->remove_a_css_rule(index);
+    if (!result.is_exception()) {
+        if (m_style_sheet_list) {
+            m_style_sheet_list->bump_generation();
+            m_style_sheet_list->document().invalidate_style();
+        }
+    }
+    return result;
 }
 
 // https://www.w3.org/TR/cssom/#dom-cssstylesheet-removerule
@@ -67,4 +85,9 @@ bool CSSStyleSheet::evaluate_media_queries(HTML::Window const& window)
     return m_rules->evaluate_media_queries(window);
 }
 
+void CSSStyleSheet::set_style_sheet_list(Badge<StyleSheetList>, StyleSheetList* list)
+{
+    m_style_sheet_list = list;
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h
index 45e255d029..3b7a9a402f 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h
@@ -50,12 +50,16 @@ public:
     // Returns whether the match state of any media queries changed after evaluation.
     bool evaluate_media_queries(HTML::Window const&);
 
+    void set_style_sheet_list(Badge<StyleSheetList>, StyleSheetList*);
+
 private:
     explicit CSSStyleSheet(NonnullRefPtrVector<CSSRule>);
 
     NonnullRefPtr<CSSRuleList> m_rules;
 
     WeakPtr<CSSRule> m_owner_css_rule;
+
+    WeakPtr<StyleSheetList> m_style_sheet_list;
 };
 
 }
diff --git a/Userland/Libraries/LibWeb/CSS/StyleSheetList.cpp b/Userland/Libraries/LibWeb/CSS/StyleSheetList.cpp
index f4945c1e8a..23d6dd96d6 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleSheetList.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleSheetList.cpp
@@ -12,6 +12,7 @@ namespace Web::CSS {
 void StyleSheetList::add_sheet(NonnullRefPtr<CSSStyleSheet> sheet)
 {
     VERIFY(!m_sheets.contains_slow(sheet));
+    sheet->set_style_sheet_list({}, this);
     m_sheets.append(move(sheet));
 
     ++m_generation;
@@ -20,6 +21,7 @@ void StyleSheetList::add_sheet(NonnullRefPtr<CSSStyleSheet> sheet)
 
 void StyleSheetList::remove_sheet(CSSStyleSheet& sheet)
 {
+    sheet.set_style_sheet_list({}, nullptr);
     m_sheets.remove_first_matching([&](auto& entry) { return &*entry == &sheet; });
 
     ++m_generation;
diff --git a/Userland/Libraries/LibWeb/CSS/StyleSheetList.h b/Userland/Libraries/LibWeb/CSS/StyleSheetList.h
index 83622557be..70eb915738 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleSheetList.h
+++ b/Userland/Libraries/LibWeb/CSS/StyleSheetList.h
@@ -16,6 +16,7 @@ namespace Web::CSS {
 
 class StyleSheetList
     : public RefCounted<StyleSheetList>
+    , public Weakable<StyleSheetList>
     , public Bindings::Wrappable {
 public:
     using WrapperType = Bindings::StyleSheetListWrapper;
@@ -45,6 +46,9 @@ public:
     int generation() const { return m_generation; }
     void bump_generation() { ++m_generation; }
 
+    DOM::Document& document() { return m_document; }
+    DOM::Document const& document() const { return m_document; }
+
 private:
     explicit StyleSheetList(DOM::Document&);
 
diff --git a/Userland/Libraries/LibWeb/Forward.h b/Userland/Libraries/LibWeb/Forward.h
index 3e39a26ffe..45f75c15b9 100644
--- a/Userland/Libraries/LibWeb/Forward.h
+++ b/Userland/Libraries/LibWeb/Forward.h
@@ -73,6 +73,7 @@ class StringStyleValue;
 class StyleComputer;
 class StyleProperties;
 class StyleSheet;
+class StyleSheetList;
 class StyleValue;
 class StyleValueList;
 class Supports;