diff --git a/src/types.ts b/src/types.ts
index 95f1bb9..9eb900f 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -54,7 +54,7 @@ export type CFDBalance = {
   longFundingRatePerDay: string
   shortFundingRatePerSecond: string
   shortFundingRatePerDay: string
-  stopOutPrice?: string
+  stopOutPrice: string | undefined
 }
 
 export type Order = {