Cactus doesn't break when growing up next to a block

(Its the the same for creative and survival)

I've made an automatic cactus farm a while ago and it worked in the 0.6.1 but since i've updated to 0.7.0 the cactus wont break when growing next to a block,
It does break if you Place a block next to it when it is for example 2 high but if it grows up next to a block that was placed before it wont break and it will be stuck. My cactus farm still works but just 35% of the cactus fall down, the others are stuck.