nvcc: "Command-line error: missing source file name"

What does this mean?

This is the command I am trying:

C:\Users\Vexal\Documents>nvcc -ptx phong.cu -I"C:\Program Files\NVIDIA Corporat
ion\OptiX SDK 2.1.0\include" -I"C:\Program Files (x86)\Microsoft Visual Studio 1
0.0\VC\include" --machine 32

It correctly generates a .ptx file if I attempt to run nvcc on a blank .cu file. Does anyone know what this error could refer to? I tried searching Google for the error, and the results were either not relevant enough, or over my head, I can’t tell. I am new to nvcc and am stumped.

Actually, I now get the error when attempting to compile any .cu file, even if it is blank. I get the same error if I leave out the ‘-ptx’ option.