diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 60e73a4..2ba8e2a 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -6,7 +6,7 @@ export interface DocumentTypeDecoration<TResult, TVariables> {
    * and that the Result is assignable to whatever you pass your result to. The method is never actually
    * implemented, but the type is valid because we list it as optional
    */
-  __apiType?: (variables: TVariables) => TResult;
+  __apiType?(variables: TVariables): TResult;
 }
 
 export interface TypedDocumentNode<