Cannot Calculate Jacobian of Matrix Multiplication

Consider the following operation `M * x` where `A` is a matrix and `x` a vector.

Here is what I thought should work, but didn't.  

``` 
@variables M[1:3, 1:3], x[1:3] 
Symbolics.jacobian(M*x, reshape(M, 9)) # Does not work 
Symbolics.jacobian(M*x, [M[1,1], M[1,2]]) # Does not work
```