inputminted can't find the source code file

I’m trying to import a Python script into my LaTeX document using inputminted, but it only works if I use the absolute path.
E.g. this works:
inputminted{python}{C:/Documents/example.py}
This does not, although the .tex and the .py file are in the same folder:
inputminted{python}{example.py}

The error is:

! Package minted Error: Missing Pygments output; inputminted was  
probably given a file that does not exist--otherwise, you may need  
the outputdir package option, or may be using an incompatible build tool,  
or may be using frozencache with a missing file.

I’m using TeXworks with the default pdfLaTeX+MakeIndex+BibTex builder, but added --tex-option=--shell-escape for minted to work.

Any ideas why I cannot use this relative path?