diff --git a/lib.go b/lib.go
index 59c9b0f..53fc0e2 100644
--- a/lib.go
+++ b/lib.go
@@ -7,6 +7,7 @@ import (
 	"io"
 	"net/http"
 	"strings"
+	"fmt"
 )
 
 type Cli struct {
@@ -57,7 +58,7 @@ func (c *Cli) Do(method string, strurl string, body []byte) (*http.Response, err
 	}
 	res,err:= c.cli.Do(req)
 	if err==nil && res.StatusCode >=400{
-		return nil, errors.New("Http return code - %d: %s",res.StatusCode,res.Status)
+		return nil, errors.New(fmt.Sprintf("Http return code - %d: %s",res.StatusCode,res.Status))
 	}
 	return res,err
 }