Derivative Disagreement

When I take the derivative, d/dx(((1/√(5))((φ^x )-(1-φ)^x )) where φ=(1+√(5))/2 by hand I achieve: (1/√5)((ln(φ)(φ^x )-ln(1-φ)(1-φ)^x ).

However, when I check this with wolfram|alpha, it gives me: (1/√5)(log(φ)(φ^x )-((1-φ)^x ) (log(φ-1)+i*pi)).

Where does alpha get the ipi? I'm guessing it is related to ln(-1)=ipi from Euler's identity, but I don't know why it is here. Any thoughts? Did I do something wrong?