diff --git a/denops/@ddc-sources/file.ts b/denops/@ddc-sources/file.ts
index a00844b..e8a4521 100644
--- a/denops/@ddc-sources/file.ts
+++ b/denops/@ddc-sources/file.ts
@@ -66,7 +66,7 @@ export class Source extends BaseSource<Params> {
       "ddc_file#internal#get_pos",
       args.context.input,
       args.sourceParams.filenameChars,
-    );
+    ) as number;
     return Promise.resolve(completePos);
   }