/give click event on signs with JSON not updating

when i set a sign with the blockdata: /blockdata ~ ~1 ~ {Text1:"{text:give,clickEvent:{action:run_command,value:'/give @p stone'}}"}

and i right click on it, the give animation shows and i recive a stone for each click, but my inventory didn't update. if i click 10 times, i will not have any stone on my inventory, but, if i after the 10 clicks, use the command /give @p minecraft:stone ; in my inventory will appear 11 stones( 10 from the sign click and 1 from the command).
i hope you undestand my bad english