Is there MD tag in output of bwa?

[YuanHank]

Hi now I'm running same pipeline using chira, which is based on bwa alignment. Two pipeline use the same version of chira with different version of bwa. One using version 0.7.5a-r405,and another one using version 0.7.12-r1039. The ouput .bam file conduct MD tag on the version 0.7.12-r1039 but not on version 0.7.5a-r405. I wonder if this is nomal on version difference?