diff --git a/substrate/frame/example-offchain-worker/src/lib.rs b/substrate/frame/example-offchain-worker/src/lib.rs
index 644e1ca299..9b63ffa663 100644
--- a/substrate/frame/example-offchain-worker/src/lib.rs
+++ b/substrate/frame/example-offchain-worker/src/lib.rs
@@ -86,10 +86,19 @@ pub mod crypto {
 	use sp_runtime::{
 		app_crypto::{app_crypto, sr25519},
 		traits::Verify,
+		MultiSignature, MultiSigner,
 	};
 	app_crypto!(sr25519, KEY_TYPE);
 
 	pub struct TestAuthId;
+
+	impl frame_system::offchain::AppCrypto<MultiSigner, MultiSignature> for TestAuthId {
+		type RuntimeAppPublic = Public;
+		type GenericSignature = sp_core::sr25519::Signature;
+		type GenericPublic = sp_core::sr25519::Public;
+	}
+
+	// implemented for mock runtime in test
 	impl frame_system::offchain::AppCrypto<<Sr25519Signature as Verify>::Signer, Sr25519Signature>
 		for TestAuthId
 	{