i think execute is broken

i did:/execute if block 297 4 933 stone
it says:Unknown command at position 32: ... 933 stone<--[HERE]
so i did:/execute if block 297 4 933 stone say hey
it says:Incorrect argument for command at position 33: ...933 stone <--[HERE]
but I thought I had to do this:
/execute (if|unless) block <x y z> <block> <chained command>