Replace text

I’m trying to replace text in a file that is like:

keepthis=something

I want to replace what is after the =

So far I have this:

powershell -Command “(gc test.txt) -replace ‘keepthis=.*?’, ‘keepthis=thisinstead’ | Set-Content test.txt

But with that I end up with:

keepthis=thisinsteadsomething

but I need:

keepthis=thisinstead