diff --git a/Libraries/LibWeb/CSS/CSSStyleProperties.cpp b/Libraries/LibWeb/CSS/CSSStyleProperties.cpp
index 0c60ffdac1f..b621c4990a9 100644
--- a/Libraries/LibWeb/CSS/CSSStyleProperties.cpp
+++ b/Libraries/LibWeb/CSS/CSSStyleProperties.cpp
@@ -44,7 +44,7 @@ GC::Ref<CSSStyleProperties> CSSStyleProperties::create(JS::Realm& realm, Vector<
     return realm.create<CSSStyleProperties>(realm, Computed::No, Readonly::No, convert_declarations_to_specified_order(properties), move(custom_properties), OptionalNone {});
 }
 
-GC::Ref<CSSStyleProperties> CSSStyleProperties::create_resolved_style(DOM::ElementReference element_reference)
+GC::Ref<CSSStyleProperties> CSSStyleProperties::create_resolved_style(JS::Realm& realm, Optional<DOM::ElementReference> element_reference)
 {
     // https://drafts.csswg.org/cssom/#dom-window-getcomputedstyle
     // 6.  Return a live CSSStyleProperties object with the following properties:
@@ -54,7 +54,6 @@ GC::Ref<CSSStyleProperties> CSSStyleProperties::create_resolved_style(DOM::Eleme
     //     parent CSS rule: Null.
     //     owner node: obj.
     // AD-HOC: Rather than instantiate with a list of decls, they're generated on demand.
-    auto& realm = element_reference.element().realm();
     return realm.create<CSSStyleProperties>(realm, Computed::Yes, Readonly::Yes, Vector<StyleProperty> {}, HashMap<FlyString, StyleProperty> {}, move(element_reference));
 }
 
diff --git a/Libraries/LibWeb/CSS/CSSStyleProperties.h b/Libraries/LibWeb/CSS/CSSStyleProperties.h
index 51c6e0b1da7..f2f7da8feca 100644
--- a/Libraries/LibWeb/CSS/CSSStyleProperties.h
+++ b/Libraries/LibWeb/CSS/CSSStyleProperties.h
@@ -22,7 +22,7 @@ class CSSStyleProperties
 public:
     [[nodiscard]] static GC::Ref<CSSStyleProperties> create(JS::Realm&, Vector<StyleProperty>, HashMap<FlyString, StyleProperty> custom_properties);
 
-    [[nodiscard]] static GC::Ref<CSSStyleProperties> create_resolved_style(DOM::ElementReference);
+    [[nodiscard]] static GC::Ref<CSSStyleProperties> create_resolved_style(JS::Realm&, Optional<DOM::ElementReference>);
     [[nodiscard]] static GC::Ref<CSSStyleProperties> create_element_inline_style(DOM::ElementReference, Vector<StyleProperty>, HashMap<FlyString, StyleProperty> custom_properties);
 
     virtual ~CSSStyleProperties() override = default;
diff --git a/Libraries/LibWeb/DOM/Element.cpp b/Libraries/LibWeb/DOM/Element.cpp
index 9c8f914d067..4b83bd546c0 100644
--- a/Libraries/LibWeb/DOM/Element.cpp
+++ b/Libraries/LibWeb/DOM/Element.cpp
@@ -775,7 +775,7 @@ CSS::RequiredInvalidationAfterStyleChange Element::recompute_inherited_style()
 
 GC::Ref<CSS::ComputedProperties> Element::resolved_css_values(Optional<CSS::PseudoElement> type)
 {
-    auto element_computed_style = CSS::CSSStyleProperties::create_resolved_style({ *this, type });
+    auto element_computed_style = CSS::CSSStyleProperties::create_resolved_style(realm(), ElementReference { *this, type });
     auto properties = heap().allocate<CSS::ComputedProperties>();
 
     for (auto i = to_underlying(CSS::first_property_id); i <= to_underlying(CSS::last_property_id); ++i) {
diff --git a/Libraries/LibWeb/Editing/Internal/Algorithms.cpp b/Libraries/LibWeb/Editing/Internal/Algorithms.cpp
index da87a090e87..dd8f76ffcb3 100644
--- a/Libraries/LibWeb/Editing/Internal/Algorithms.cpp
+++ b/Libraries/LibWeb/Editing/Internal/Algorithms.cpp
@@ -4741,7 +4741,7 @@ Optional<NonnullRefPtr<CSS::CSSStyleValue const>> resolved_value(GC::Ref<DOM::No
         return {};
 
     // Retrieve resolved style value
-    auto resolved_css_style_declaration = CSS::CSSStyleProperties::create_resolved_style({ static_cast<DOM::Element&>(*element) });
+    auto resolved_css_style_declaration = CSS::CSSStyleProperties::create_resolved_style(element->realm(), DOM::ElementReference { static_cast<DOM::Element&>(*element) });
     auto optional_style_property = resolved_css_style_declaration->property(property_id);
     if (!optional_style_property.has_value())
         return {};
diff --git a/Libraries/LibWeb/HTML/Window.cpp b/Libraries/LibWeb/HTML/Window.cpp
index bc4eca33973..ce4a17bf2eb 100644
--- a/Libraries/LibWeb/HTML/Window.cpp
+++ b/Libraries/LibWeb/HTML/Window.cpp
@@ -1273,7 +1273,7 @@ GC::Ref<CSS::CSSStyleDeclaration> Window::get_computed_style(DOM::Element& eleme
     // 1. Let doc be elt’s node document.
 
     // 2. Let obj be elt.
-    DOM::ElementReference object { element };
+    Optional<DOM::ElementReference> object { element };
 
     // 3. If pseudoElt is provided, is not the empty string, and starts with a colon, then:
     if (pseudo_element.has_value() && pseudo_element.value().starts_with(':')) {
@@ -1281,8 +1281,8 @@ GC::Ref<CSS::CSSStyleDeclaration> Window::get_computed_style(DOM::Element& eleme
         auto type = parse_pseudo_element_selector(CSS::Parser::ParsingParams(associated_document()), pseudo_element.value());
 
         // 2. If type is failure, or is a ::slotted() or ::part() pseudo-element, let obj be null.
-        // FIXME: We can't pass a null element to CSSStyleProperties::create_resolved_style()
         if (!type.has_value()) {
+            object = {};
         }
         // 3. Otherwise let obj be the given pseudo-element of elt.
         else {
@@ -1311,7 +1311,7 @@ GC::Ref<CSS::CSSStyleDeclaration> Window::get_computed_style(DOM::Element& eleme
     //        Null.
     //    owner node
     //        obj.
-    return CSS::CSSStyleProperties::create_resolved_style(move(object));
+    return CSS::CSSStyleProperties::create_resolved_style(element.realm(), move(object));
 }
 
 // https://w3c.github.io/csswg-drafts/cssom-view/#dom-window-matchmedia