scipy/scipy — pull request #3770 by WarrenWeckesser (2014-07-04 23:42:57+00:00)
Title: BUG: signal: In lfilter_zi, b was not rescaled correctly when a[0] was not 1.

The problem was reported here: https://github.com/scipy/scipy/commit/8d4665f77ffab58d40ef712a36030450007b48e0#commitcomment-6889990