qmake INSTALLS target does not work with spaces in the path name, strips quotes

In Windows XP, with a pro file, and PROGRAMFILES_HOME environment variable set to C:\Program Files

target.path = "$$(PROGRAMFILES_HOME)"
target.files = ./src/*.h
INSTALLS += target

Do a qmake; nmake install. get the following output

copy /y c:\example\src\example.h c:\Program Files
The syntax of the command is incorrect.

If I wrap the destination directory in quotes copy /y c:\example\src\example.h "c:\Program Files", the copy command works. The quotes in the .pro file in the INSTALLS section are being stripped.