diff --git a/src/models/stratum-messages/MiningSubmitMessage.ts b/src/models/stratum-messages/MiningSubmitMessage.ts
index fdfb155..4e254da 100644
--- a/src/models/stratum-messages/MiningSubmitMessage.ts
+++ b/src/models/stratum-messages/MiningSubmitMessage.ts
@@ -1,5 +1,5 @@
 import { Expose, Transform } from 'class-transformer';
-import { ArrayMaxSize, ArrayMinSize, IsArray, IsOptional, IsString } from 'class-validator';
+import { ArrayMaxSize, ArrayMinSize, IsArray, IsString } from 'class-validator';
 
 import { eRequestMethod } from '../enums/eRequestMethod';
 import { StratumBaseMessage } from './StratumBaseMessage';
@@ -43,10 +43,9 @@ export class MiningSubmitMessage extends StratumBaseMessage {
     public nonce: string
 
     @Expose()
-    @IsOptional()
     @IsString()
     @Transform(({ value, key, obj, type }) => {
-        return obj.params[5];
+        return obj.params[5] == null ? 0 : obj.params[5];
     })
     public versionMask?: string | null;