qmake prints 'Access is denied' when it actually can't find the .pro file

Qmake prints a misleading error message when run for a directory that either contains no, or multiple, pro files:

D:\dev\qbs\1.1\qt-stable-msvc-2012-32>qmake ..\src
Cannot read D:/dev/qbs/1.1/src: Access is denied.

What I'd expect

some more helpful error message, like "Cannot find .pro file".