Movement bug with knight

I'm playing a civ5 game and I have a knight in front of an enemy canon. The knight has 3 moves remaining and I want to attack the canon and pull away a hex out of range of city fire. The strange thing is, I hit the canon and all 3 moves are taken up. I know about zone of control and there are no other adjacent enemy units. Enemy does not have the great wall as I just moved a rifleman into enemy territory with one move remaining. The hex occupied by the enemy is a forest grassland hill. The hex occupied by my knight is grassland road. The enemy is Hiawatha and I'm playing as Ethiopia.

Pictures:
http://postimage.org/image/brsgv2oj3/
http://postimage.org/image/h2z585p13/

 

Flat terrain takes 1 movement. Hills take 1 additional movement. Forest add 1 additional movement. So it takes 3 movement to attack the cannon.