Solr 9 Windows: how to index directory with spaces in name

I'm using post.jar (on Windows 10) to index directories. I cannot figure out the syntax to use for directories with spaces in their names. Here is an example (using single quotes):

X:\yada\solr-9.0.0> java -jar -Dc=cd1 -Dauto -Drecursive=5 .\post.jar 'P:\projects\blah\spaces in this dir name\*'

I've tried escaping the spaces, putting the path inside double and single quotes, backticks.