• 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 10.14.3
• Poetry version: 0.12.11
• Link of a Gist with the contents of your pyproject.toml file: N/A

Issue

1!2019.2.12 is requested but 1!2015.2.1 is installed:

$ poetry new demo
$ cd demo
$ poetry add "foursquare==1\!2019.2.12"
Creating virtualenv demo-py3.7 in /private/tmp/demo/.venv

Updating dependencies
Resolving dependencies... (0.2s)
Package operations: 13 installs, 0 updates, 0 removals

Writing lock file

  - Installing certifi (2018.11.29)
  ...
  - Installing foursquare (1!2015.2.1)
  ...

I see code that seems to support this, but no tests: https://github.com/sdispater/poetry/search?q=epoch&unscoped_q=epoch