diff --git a/lib/av_client/types.ts b/lib/av_client/types.ts
index 3ac02d80..4151eec6 100644
--- a/lib/av_client/types.ts
+++ b/lib/av_client/types.ts
@@ -9,7 +9,7 @@ export interface IAVClient {
   spoilBallot(): Promise<string>
   castBallot (affidavit: Affidavit): Promise<BallotBoxReceipt>
   purgeData(): void
-  challengeBallot(): void
+  challengeBallot(): Promise<void>
 }
 
 /**
@@ -288,4 +288,4 @@ interface Service {
 interface AffidavitConfig {
   curve: string;
   encryptionKey: string;
-}
\ No newline at end of file
+}