JIRA Issue doesn't accept more than 6 digits (BB-15773)

Bitbucket with the "Jira Link" feature, appears to only recognise jira issue keys with issue numbers up to 6 digits long. Longer numeric-parts of the issue key are incorrectly interpreted as commit hashes.

*HOST is the project key.

Bitbucket correctly recognises the following issue ids:

HOST-1234
HOST-12345
HOST-123456
The entire id appears as a link and correctly links to Jira.
However, as soon as the number part is longer than 6 digits, e.g.:

HOST-1234567
HOST-12345678