diff --git a/Libraries/LibWeb/CSS/CSSImportRule.idl b/Libraries/LibWeb/CSS/CSSImportRule.idl
index fd8b073129b..d474386d076 100644
--- a/Libraries/LibWeb/CSS/CSSImportRule.idl
+++ b/Libraries/LibWeb/CSS/CSSImportRule.idl
@@ -7,7 +7,7 @@
 interface CSSImportRule : CSSRule {
     readonly attribute USVString href;
     // FIXME: [SameObject, PutForwards=mediaText] readonly attribute MediaList media;
-    [SameObject, ImplementedAs=style_sheet_for_bindings] readonly attribute CSSStyleSheet styleSheet;
+    [SameObject, ImplementedAs=style_sheet_for_bindings] readonly attribute CSSStyleSheet? styleSheet;
     [FIXME] readonly attribute CSSOMString? layerName;
     [FIXME] readonly attribute CSSOMString? supportsText;
 };