title: Warning: The lock file is not up to date with the latest changes in pyproject.toml
body: <p>When I am using a poetry command with Python 3.7, in my case:</p>
  
  <pre><code>poetry export -f requirements.txt
  </code></pre>
  
  <p>I am getting the following error:</p>
  
  <pre><code>Warning: The lock file is not up to date with the latest changes in pyproject.toml. You may be getting outdated dependencies. Run update to update them.
  </code></pre>
  
  <p>So far clear, but if I run poetry update it upgrades my dependencies, which is not what I want at this time for my project. If I run poetry lock instead, it still upgrades dependencies.</p>
  
  <p>How can I work around this?</p>