diff --git a/backend/cmd/main.go b/backend/cmd/main.go
index 430a647..aa70b74 100644
--- a/backend/cmd/main.go
+++ b/backend/cmd/main.go
@@ -39,7 +39,7 @@ func main() {
 			},
 			&cli.StringFlag{
 				Name:  "chain-api-url",
-				Value: "http://localhost:3000",
+				Value: "http://localhost:3000/api",
 			},
 
 			// rest
diff --git a/backend/internal/usecase/interactors/chain/chain.go b/backend/internal/usecase/interactors/chain/chain.go
index 6259335..158f1e5 100644
--- a/backend/internal/usecase/interactors/chain/chain.go
+++ b/backend/internal/usecase/interactors/chain/chain.go
@@ -264,6 +264,10 @@ func (i *chainInteractor) PubKey(ctx context.Context, user *models.User) ([]byte
 
 	pubKeyStr := string(respBody)[2:]
 
+	if pubKeyStr == "" {
+		return nil, fmt.Errorf("error empty public key")
+	}
+
 	return common.Hex2Bytes(pubKeyStr), nil
 }