diff --git a/libs/log/tmfmt_logger.go b/libs/log/tmfmt_logger.go
index c6004cc62..b9389b18e 100644
--- a/libs/log/tmfmt_logger.go
+++ b/libs/log/tmfmt_logger.go
@@ -98,7 +98,7 @@ func (l tmfmtLogger) Log(keyvals ...interface{}) error {
 	//     D										- first character of the level, uppercase (ASCII only)
 	//     [2016-05-02|11:06:44.322]    - our time format (see https://golang.org/src/time/format.go)
 	//     Stopping ...					- message
-	enc.buf.WriteString(fmt.Sprintf("%c[%s] %-44s ", lvl[0]-32, time.Now().Format("2006-01-02|15:04:05.000"), msg))
+	fmt.Fprintf(&enc.buf, "%c[%s] %-44s ", lvl[0]-32, time.Now().Format("2006-01-02|15:04:05.000"), msg)
 
 	if module != unknown {
 		enc.buf.WriteString("module=" + module + " ")