diff --git a/layout/style/ServoBindings.h b/layout/style/ServoBindings.h
index 0b131851ce9c..23a9d2bbf571 100644
--- a/layout/style/ServoBindings.h
+++ b/layout/style/ServoBindings.h
@@ -102,6 +102,9 @@ using mozilla::dom::StyleChildrenIterator;
 DECL_ARC_REF_TYPE_FOR(ServoComputedValues)
 DECL_ARC_REF_TYPE_FOR(RawServoStyleSheet)
 DECL_ARC_REF_TYPE_FOR(RawServoDeclarationBlock)
+// This is a reference to a reference of RawServoDeclarationBlock, which
+// corresponds to Option<&Arc<RawServoDeclarationBlock>> in Servo side.
+DECL_NULLABLE_BORROWED_REF_TYPE_FOR(RawServoDeclarationBlockStrong)
 
 DECL_OWNED_REF_TYPE_FOR(RawServoStyleSet)
 DECL_NULLABLE_OWNED_REF_TYPE_FOR(StyleChildrenIterator)