blink-diff shows Differences as '0%' & returns 'FAIL' as result

[sjethvani]

I have been using blink-diff for image comparison of selenium captured screens . For some comparisons I have noticed that blink-diff gives result as 'FAIL' however when looking at percentage difference , it shows '0%' . Doesn't that seem strange .
Comparisons having '0%' differences should be marked as 'PASS' , however blink-diff returns 'FAIL' ...

Below is the command line I use for doing screen comparison .

D:\>node d:\node_modules\blink-diff\bin\blink-diff --verbose --threshold-
type percent --threshold 0% --output compare1.png previous_release1.png next_release1.png
Blink-Diff 1.0.13
Copyright (C) 2014 Yahoo! Inc.
Images are visibly different
29 pixels are different
Wrote differences to compare1.png
Time: 498.177ms
Differences: 29 (0%)
FAIL