diff --git a/lib/types/customers.d.ts b/lib/types/customers.d.ts
index c18d5c6..d42df75 100644
--- a/lib/types/customers.d.ts
+++ b/lib/types/customers.d.ts
@@ -25,7 +25,7 @@ export declare namespace Customers {
          *
          * `1` (default): If a customer with the same details already exists, throws an error.
          */
-        fail_existing?: boolean | 0 | 1;
+        fail_existing?: "0" | "1";
         /**
          * Customer's GST number, if available
          */
@@ -245,4 +245,4 @@ declare function customers(api: any): {
      fetchEligibility(eligibilityId: string): Promise<Partial<Customers.RazorpayCustomerEligibility>>
 }
 
-export default customers
\ No newline at end of file
+export default customers