HaplotypeCaller not generating DP field

I am using GATK 2.5, and am calling HaplotypeCaller as

java -Xmx4g -jar GenomeAnalysisTK.jar -R ucsc.hg19.fasta -T HaplotypeCaller -I sample.bam -o hap.vcf -L subset.bed -dt NONE -D dbsnp_137.b37_addChr.vcf -filterNoBases -A Coverage -A DepthPerAlleleBySample

In the output vcf file, in the FORMAT field, I have GT:AD:GQ:PL. DP is lost. Even though it is specified in the header. UnifiedGenotyper is working fine, and producing DP information. Any ideas on what is wrong?

Thanks