basic tutorial 13: code doesn't work as written

After running basic-tutorial-13, then interacting to do 'p'ause, 'd'irection, and then 'n'ext frame, the movie still moves forward rather than backwards.

An example session:

./basic-tutorial-13 
USAGE: Choose one of the following options, then press enter:
 'P' to toggle between PAUSE and PLAY
 'S' to increase playback speed, 's' to decrease playback speed
 'D' to toggle playback direction
 'N' to move to next frame (in the current direction, better in PAUSE)
 'Q' to quit
p
Setting state to PAUSE
d
Current rate: -1
n
Stepping one frame
n
Stepping one frame
n

I've tested this against gstreamer 1.14 and 1.16, both simply step forward one frame at a time.