When changing the Test Step attachments from a Test definition, previous Test Runs are affected and they shouldn't

When changing the Test Step attachments from a Test definition, previous Test Runs are affected and they shouldn't

1. Create a Test.
2. Attach some file to a Test Step.
3. Run the Test.
4. Replace the Test Step's attachment with another file.
5. Check the Test Execution details.

Expected behavior:
Test Execution shows the old attachment.

Actual behavior:
Test Execution shows the new attachment (even though the Test Run was not reset).