-C argument to CMake doesn't work

From a terminal, I can pass cmake an initial cache file like this:

cmake -C /path/to/InitialCache.txt /path/to/source

and it works correctly.

However, in QtCreator, when I File->Open a CMakeLists.txt file, and set the Arguments text box to

-C /patth/to/InitialCache.txt

I get:

"loading initial cache file /path/to/InitialCache.txt
CMake Error: The source directory "/path/to/InitialCache.txt" is a file, not a directory."

Any thoughts on this?