In the following block:

#+BEGIN_SRC python :results value :session
def f():
    return 5
f()
#+END_SRC

It gives the message

"Code block returned no value"

when trying to run it. This is clearly not intended behavior, as

#+BEGIN_SRC python :results value :session
def f():
    return 5
f()
10
#+END_SRC

#+RESULTS:
: 10

works perfectly fine. Does anyone else have this issue?