diff --git a/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp b/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
index f6ac28a08e..a86b86c1ac 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
+++ b/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
@@ -17,9 +17,9 @@
 
 namespace Web::CSS {
 
-CSSRuleList* CSSRuleList::create(JS::Realm& realm, JS::MarkedVector<CSSRule*> const& rules)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<CSSRuleList>> CSSRuleList::create(JS::Realm& realm, JS::MarkedVector<CSSRule*> const& rules)
 {
-    auto rule_list = realm.heap().allocate<CSSRuleList>(realm, realm).release_allocated_value_but_fixme_should_propagate_errors();
+    auto rule_list = MUST_OR_THROW_OOM(realm.heap().allocate<CSSRuleList>(realm, realm));
     for (auto* rule : rules)
         rule_list->m_rules.append(*rule);
     return rule_list;
@@ -30,9 +30,9 @@ CSSRuleList::CSSRuleList(JS::Realm& realm)
 {
 }
 
-CSSRuleList* CSSRuleList::create_empty(JS::Realm& realm)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<CSSRuleList>> CSSRuleList::create_empty(JS::Realm& realm)
 {
-    return realm.heap().allocate<CSSRuleList>(realm, realm).release_allocated_value_but_fixme_should_propagate_errors();
+    return MUST_OR_THROW_OOM(realm.heap().allocate<CSSRuleList>(realm, realm));
 }
 
 JS::ThrowCompletionOr<void> CSSRuleList::initialize(JS::Realm& realm)
diff --git a/Userland/Libraries/LibWeb/CSS/CSSRuleList.h b/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
index 726a7c5f9e..76f56f4a30 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
@@ -23,8 +23,8 @@ class CSSRuleList : public Bindings::LegacyPlatformObject {
     WEB_PLATFORM_OBJECT(CSSRuleList, Bindings::LegacyPlatformObject);
 
 public:
-    static CSSRuleList* create(JS::Realm&, JS::MarkedVector<CSSRule*> const&);
-    static CSSRuleList* create_empty(JS::Realm&);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<CSSRuleList>> create(JS::Realm&, JS::MarkedVector<CSSRule*> const&);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<CSSRuleList>> create_empty(JS::Realm&);
 
     ~CSSRuleList() = default;
 
diff --git a/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp b/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
index f02b6dc81a..402dd17b45 100644
--- a/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
+++ b/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
@@ -127,8 +127,8 @@ CSSStyleSheet* Parser::parse_as_css_stylesheet(Optional<AK::URL> location)
             rules.append(rule);
     }
 
-    auto* rule_list = CSSRuleList::create(m_context.realm(), rules);
-    return CSSStyleSheet::create(m_context.realm(), *rule_list, *MediaList::create(m_context.realm(), {}), move(location));
+    auto rule_list = CSSRuleList::create(m_context.realm(), rules).release_value_but_fixme_should_propagate_errors();
+    return CSSStyleSheet::create(m_context.realm(), rule_list, *MediaList::create(m_context.realm(), {}), move(location));
 }
 
 Optional<SelectorList> Parser::parse_as_selector(SelectorParsingMode parsing_mode)
@@ -3057,8 +3057,8 @@ CSSRule* Parser::convert_to_rule(NonnullRefPtr<Rule> rule)
                 if (auto* child_rule = convert_to_rule(raw_rule))
                     child_rules.append(child_rule);
             }
-            auto* rule_list = CSSRuleList::create(m_context.realm(), child_rules);
-            return CSSMediaRule::create(m_context.realm(), *MediaList::create(m_context.realm(), move(media_query_list)), *rule_list).release_value_but_fixme_should_propagate_errors();
+            auto rule_list = CSSRuleList::create(m_context.realm(), child_rules).release_value_but_fixme_should_propagate_errors();
+            return CSSMediaRule::create(m_context.realm(), *MediaList::create(m_context.realm(), move(media_query_list)), rule_list).release_value_but_fixme_should_propagate_errors();
         }
         if (rule->at_rule_name().equals_ignoring_case("supports"sv)) {
             auto supports_tokens = TokenStream { rule->prelude() };
@@ -3081,8 +3081,8 @@ CSSRule* Parser::convert_to_rule(NonnullRefPtr<Rule> rule)
                     child_rules.append(child_rule);
             }
 
-            auto* rule_list = CSSRuleList::create(m_context.realm(), child_rules);
-            return CSSSupportsRule::create(m_context.realm(), supports.release_nonnull(), *rule_list);
+            auto rule_list = CSSRuleList::create(m_context.realm(), child_rules).release_value_but_fixme_should_propagate_errors();
+            return CSSSupportsRule::create(m_context.realm(), supports.release_nonnull(), rule_list);
         }
 
         // FIXME: More at rules!
@@ -7396,8 +7396,10 @@ namespace Web {
 
 CSS::CSSStyleSheet* parse_css_stylesheet(CSS::Parser::ParsingContext const& context, StringView css, Optional<AK::URL> location)
 {
-    if (css.is_empty())
-        return CSS::CSSStyleSheet::create(context.realm(), *CSS::CSSRuleList::create_empty(context.realm()), *CSS::MediaList::create(context.realm(), {}), location);
+    if (css.is_empty()) {
+        auto rule_list = CSS::CSSRuleList::create_empty(context.realm()).release_value_but_fixme_should_propagate_errors();
+        return CSS::CSSStyleSheet::create(context.realm(), rule_list, *CSS::MediaList::create(context.realm(), {}), location);
+    }
     CSS::Parser::Parser parser(context, css);
     return parser.parse_as_css_stylesheet(location);
 }