diff --git a/rpc/jeth.go b/rpc/jeth.go
index 757f6b7eb5..ae2603ae4a 100644
--- a/rpc/jeth.go
+++ b/rpc/jeth.go
@@ -44,11 +44,12 @@ func NewJeth(ethApi shared.EthereumApi, re *jsre.JSRE, client comms.EthereumClie
 }
 
 func (self *Jeth) err(call otto.FunctionCall, code int, msg string, id interface{}) (response otto.Value) {
-	errObj := fmt.Sprintf("{\"message\": \"%s\", \"code\": %d}", msg, code)
-	retResponse := fmt.Sprintf("ret_response = JSON.parse('{\"jsonrpc\": \"%s\", \"id\": %v, \"error\": %s}');", shared.JsonRpcVersion, id, errObj)
+	m := shared.NewRpcErrorResponse(id, shared.JsonRpcVersion, code, fmt.Errorf(msg))
+	errObj, _ := json.Marshal(m.Error)
+	errRes, _ := json.Marshal(m)
 
-	call.Otto.Run("ret_error = " + errObj)
-	res, _ := call.Otto.Run(retResponse)
+	call.Otto.Run("ret_error = " + string(errObj))
+	res, _ := call.Otto.Run("ret_response = " + string(errRes))
 
 	return res
 }
diff --git a/rpc/shared/types.go b/rpc/shared/types.go
index 659b74bf60..dd9a60aab9 100644
--- a/rpc/shared/types.go
+++ b/rpc/shared/types.go
@@ -74,11 +74,9 @@ type ErrorObject struct {
 }
 
 // Create RPC error response, this allows for custom error codes
-func NewRpcErrorResponse(id interface{}, jsonrpcver string, errCode int, err error) *interface{} {
-	var response interface{}
-
+func NewRpcErrorResponse(id interface{}, jsonrpcver string, errCode int, err error) *ErrorResponse {
 	jsonerr := &ErrorObject{errCode, err.Error()}
-	response = ErrorResponse{Jsonrpc: jsonrpcver, Id: id, Error: jsonerr}
+	response := ErrorResponse{Jsonrpc: jsonrpcver, Id: id, Error: jsonerr}
 
 	glog.V(logger.Detail).Infof("Generated error response: %s", response)
 	return &response