• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: macOS-10.15.5-x86_64-i386-64bit
• Poetry version: 1.0.9
• Link of a Gist with the contents of your pyproject.toml file:

Issue

When I'm installing pyproject2.toml in the gist everything works fine (poetry install), but when I try to install extra dependencies in pyproject1.toml (poetry install -E dask) I receive the following error message

[RecursionError]
maximum recursion depth exceeded

I guess it could be related to #1138