diff --git a/index.d.ts b/index.d.ts
index f3e8860..1e8d062 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -7,5 +7,5 @@ declare namespace JsonSchemaToOpenapiSchema {
 declare function JsonSchemaToOpenapiSchema<T = Record<string | number, any>>(
   schema: Record<string | number, any>,
   options?: JsonSchemaToOpenapiSchema.Options
-): T;
+): Promise<T>;
 export = JsonSchemaToOpenapiSchema;