Woops, didn't explain that well. `lambdify` will default to import numpy. This fix is in `lambdarepr`, which just prints the standard lambda representation. This previously only worked one way (sympy printing, which just happened to work for `numpy.matrix` due to overloading). Unfortunately, the way that `lambdify` is set up right now, there is no coupling between the `lambdarepr` and the swapping out of functions for numpy. This was the best way I could come up with, but with some refactoring there may be a better way. Sorry for the confusion.