diff --git a/pkg/frontend/mysql_protocol.go b/pkg/frontend/mysql_protocol.go
index f9bb6baaea4c5ab03e9e72bc387af2d405ef77ad..1d37ae9fe5d338a4727185f275099ea7a3a5e873 100644
--- a/pkg/frontend/mysql_protocol.go
+++ b/pkg/frontend/mysql_protocol.go
@@ -366,7 +366,7 @@ func (mp *MysqlProtocol) appendStringLenEncOfUint64(data []byte, value uint64) [
 //return the buffer
 func (mp *MysqlProtocol) appendStringLenEncOfFloat64(data []byte, value float64, bitSize int) []byte {
 	var tmp []byte
-	tmp = strconv.AppendFloat(tmp, value, 'f', -1, bitSize)
+	tmp = strconv.AppendFloat(tmp, value, 'f', 4, bitSize)
 	return mp.appendCountOfBytesLenEnc(data, tmp)
 }