Redmine

Using Redmine 2.2.3.

I'm trying to Filter a list by a specific related issue.

The first filter option is "is" with a text box.

I have entered the task number "#1234" and I get no results.
I have entered the task with tracker "feature #1234" and get no results.

How does the "is" box work? Can I filter my issues list by one particular related issue?