Then god isn't all-knowing. If god doesn't know the decision you will make, he fails to take on the god like tenants he has been ascribed. If there are two choices and he is all-knowing, then you don't have two choices, as he knows the one that you will take. God cannot be equally as indecisive as you are if he is all knowing. This applies to all facets of life. There is only once choice, as it has been predetermined. This is the paradox of free will/pre-determination.
If I have a choice and god doesn't know which choice I will make, then I have free will. At the same time, god is not all-knowing, and, therefore, cannot be the god that Christians describe him as.