pairToBed ignores interval of length one

[hdng]

a.bedpe chr1 10 10 chr1 50 100 chr1 9 10 chr1 50 100

b.bed chr1 1 20

$ bedtools pairtobed -type either -a a.bedpe -b b.bed chr1 9 10 chr1 50 100 chr1 1 20