Using python:3.6.3-alpine based image as executor and persist_to_workspace/attach_workspace fails

When using workspace operations, I get an error:
“tar utility is not present in this image but it is required. Please install it to have workflow workspace capability.”

Output from ssh session:

$ which tar

Only after I additionally do:

$ apk add tar
$ which tar

The workspace related operations work. Is this expected? It was working w/ /bin/tar for a while now.