API 1 Requests Break Activity (BB-16199)

Assuming that the PR has a file "application/libraries/application/Entity/Project.php"
Sending this request works fine

curl -u "user:pass" -H "Content-Type: application/json" -d '

{ "content" : "Test Comment", "line_from": 136, "filename" : "application/libraries/application/Entity/Project.php" }

' https://api.bitbucket.org/1.0/repositories/user/repo/pullrequests/338/comments

Sending this request breaks the PR in the manner described.
curl -u "user:pass" -H "Content-Type: application/json" -d '

{ "content" : "Test Comment", "line_from": 136, "filename" : "/application/libraries/application/Entity/Project.php" }

' https://api.bitbucket.org/1.0/repositories/user/repo/pullrequests/338/comments

The only difference between those two calls is whether I am sending an absolute path or a relative path. (When the original requests we being sent, they weren't simply a stray slash, it was a full path on my machine).