Is it possible to create materialized view based on another materialized view in postgres?

I have a very large table and I summarize it in a materialized view. I then create an even smaller materialized view based on the earlier mview. The second mv is always showing zero rows. Is there a limitation in postgres that all mvs must be based off of a real table? I did a quick search of docs and didn't find anything.

table (millions of rows) -> mv A (thousands of rows) -> mv B (zero rows, but expected hundreds)