diff --git a/packages/types/src/types.ts b/packages/types/src/types.ts
index d4b878d3ff..adef08f823 100644
--- a/packages/types/src/types.ts
+++ b/packages/types/src/types.ts
@@ -133,6 +133,6 @@ export interface IExtrinsic extends IMethod {
   isSigned: boolean;
   method: Method;
   signature: IExtrinsicSignature;
-  addSignature (signer: Address | Uint8Array, signature: Uint8Array, nonce: AnyNumber, era?: Uint8Array): IExtrinsic;
+  addSignature (signer: Address | Uint8Array | string, signature: Uint8Array | string, nonce: AnyNumber, era?: Uint8Array): IExtrinsic;
   sign (account: KeyringPair, options: SignatureOptions): IExtrinsic;
 }