diff --git a/realtime/src/services/exchanges/index.ts b/realtime/src/services/exchanges/index.ts
index 0717c30..860a712 100644
--- a/realtime/src/services/exchanges/index.ts
+++ b/realtime/src/services/exchanges/index.ts
@@ -13,7 +13,7 @@ const exchanges: { [key: string]: IExchangeService } = {}
 const isDevExchangeConfig = (
   config: ExchangeConfig | DevExchangeConfig,
 ): config is DevExchangeConfig => {
-  return "devMockPrice" in config.config
+  return typeof config.config === "object" && "devMockPrice" in config.config
 }
 
 export const ExchangeFactory = (): ExchangeFactory => {