Attaching files to the sub-tasks from parent tasks in JIRA results in file attaching to the parent task

Steps to reproduce:
1. create a task
2. create a sub-task
3. try to attach a file to the sub-task via the [...] button (the button showed for the sub-task).
4. file is attached to the task instead of the sub-task.
Reproduced on JIRA 7.1.0. Suppose that other versions may be affected.