diff --git a/__tests__/genType.test.js b/__tests__/genType.test.js
index 573378d..883949b 100644
--- a/__tests__/genType.test.js
+++ b/__tests__/genType.test.js
@@ -6,7 +6,7 @@ it('getResourceTypeReference converts a resource path to a valid reference', ()
 
 it('getNewKeyTypeFromBatchKeySetType returns a newKey type with a valid value', () => {
     expect(getNewKeyTypeFromBatchKeySetType('bKey', "ResourcesType['foo']['bar']['baz']")).toBe(
-        `Parameters<ResourcesType['foo']['bar']['baz']['bKey']['has']>[0]`,
+        `GetSetType<ResourcesType['foo']['bar']['baz']['bKey']>`,
     );
 });
 
diff --git a/examples/swapi/swapi-loaders.ts b/examples/swapi/swapi-loaders.ts
index b78f64e..177ed8f 100644
--- a/examples/swapi/swapi-loaders.ts
+++ b/examples/swapi/swapi-loaders.ts
@@ -55,6 +55,8 @@ export type DataLoaderCodegenOptions = {
   };
 };
 
+type GetSetType<T> = T extends Set<infer U> ? U : never;
+
 /**
  * ===============================
  * BEGIN: printResourcesType()
@@ -101,9 +103,7 @@ export type LoadersType = Readonly<{
   >;
   getFilms: DataLoader<
     Omit<Parameters<ResourcesType["getFilms"]>[0], "film_ids"> & {
-      film_id: Parameters<
-        Parameters<ResourcesType["getFilms"]>[0]["film_ids"]["has"]
-      >[0];
+      film_id: GetSetType<Parameters<ResourcesType["getFilms"]>[0]["film_ids"]>;
     },
     PromisedReturnType<ResourcesType["getFilms"]>[0],
     // This third argument is the cache key type. Since we use objectHash in cacheKeyOptions, this is "string".
@@ -905,9 +905,9 @@ export default function getLoaders(
     ),
     getFilms: new DataLoader<
       Omit<Parameters<ResourcesType["getFilms"]>[0], "film_ids"> & {
-        film_id: Parameters<
-          Parameters<ResourcesType["getFilms"]>[0]["film_ids"]["has"]
-        >[0];
+        film_id: GetSetType<
+          Parameters<ResourcesType["getFilms"]>[0]["film_ids"]
+        >;
       },
       PromisedReturnType<ResourcesType["getFilms"]>[0],
       // This third argument is the cache key type. Since we use objectHash in cacheKeyOptions, this is "string".
diff --git a/src/codegen.ts b/src/codegen.ts
index 72297b8..7d50c64 100644
--- a/src/codegen.ts
+++ b/src/codegen.ts
@@ -97,6 +97,8 @@ export default function codegen(
             };
         };
 
+        type GetSetType<T> = T extends Set<infer U> ? U : never;
+
         /**
          * ===============================
          * BEGIN: printResourcesType()
diff --git a/src/genType.ts b/src/genType.ts
index 07aa885..bd9545a 100644
--- a/src/genType.ts
+++ b/src/genType.ts
@@ -15,11 +15,10 @@ function getResourceArg(resourceConfig: ResourceConfig, resourcePath: ReadonlyAr
 }
 
 /**
- * Extract the type T from a Set<T> resource (in this case a batchKey's resource)
- * using its `.has(T)`'s function paremeter type
+ * Extract the type T from a Set<T> resource (using the helper defined in codegen.ts)
  */
 export function getNewKeyTypeFromBatchKeySetType(batchKey: string, resourceArgs: string) {
-    return `Parameters<${resourceArgs}['${batchKey}']['has']>[0]`;
+    return `GetSetType<${resourceArgs}['${batchKey}']>`;
 }
 
 export function getLoaderTypeKey(resourceConfig: ResourceConfig, resourcePath: ReadonlyArray<string>) {