diff --git a/packages/groq-builder/src/types/schema-types.ts b/packages/groq-builder/src/types/schema-types.ts
index 60598bf..0958cc1 100644
--- a/packages/groq-builder/src/types/schema-types.ts
+++ b/packages/groq-builder/src/types/schema-types.ts
@@ -49,7 +49,7 @@ export type ExtractTypeNames<TResultItem> = Extract<
 >["_type"];
 
 export type RefType<referenceSymbol extends symbol, TTypeName> = {
-  [P in referenceSymbol]: TTypeName;
+  [P in referenceSymbol]?: TTypeName;
 };
 
 export type ExtractRefType<TResultItem, TQueryConfig extends QueryConfig> =