coverage bug?

output

$ coverage run --branch ./thefile.py ; coverage report
Name      Stmts   Miss Branch BrPart  Cover
-------------------------------------------
thefile       8      0      4      1    92%

thefile.py

#!/usr/bin/python

class Foo:

    def a(self, var):
        if var:
            o = lambda *a,**kw: None

        return 'a'


f = Foo()
f.a(None)
f.a('something')