diff --git a/Libraries/LibWeb/Forward.h b/Libraries/LibWeb/Forward.h
index 228f288a03a..08761758e0c 100644
--- a/Libraries/LibWeb/Forward.h
+++ b/Libraries/LibWeb/Forward.h
@@ -149,6 +149,7 @@ class CSSKeywordValue;
 class CSSLayerBlockRule;
 class CSSLayerStatementRule;
 class CSSMediaRule;
+class CSSNamespaceRule;
 class CSSNestedDeclarations;
 class CSSOKLab;
 class CSSOKLCH;