docker build requires exactly 1 argument s

Question

I'm attempting to build and tag an image from a specific Dockerfile; I'm following the published instructions for docker build, but I'm getting the following error:

"docker build" requires exactly 1 argument(s)

I use the following command:

docker build -f /full/path/to/MyDockerfile -t proj:myapp

I've tried many combinations of the above command, but the results are always the same: the above-mentioned error message. Why is this happening, despite the fact that I am following the documentation's instructions?