Minecart not going around curves

A minecart did not go around a curce

What I expected to happen was...:
for the minecart to turn with the track

What actually happened was...:
the minecart bounced back...

Steps to Reproduce:
1. place down minecart rails, giving them an S-bend
2. power the minecart
3. let it go and watch it come back to you