[0.89-test] "Index signature mismatch" error

Custom repo has been setup and is readable from the 0.88 version of the fdroidclient project. When using version 0.89-test the following message appears:

Index signature mismatch

No code has been changed. In order to reproduce, do the following:

• create a custom fdroid repo somewhere (vm/server/localhost) with a single .apk file inside
• clone the fdroidclient repo and checkout version 0.88 (use tag)
• build with Android studio, launch the app, add the new repo and pull info from the repo.
  • [RESULT] new package is shown in available app list
• checkout version 0.89-test
• build with Android studio, launch the app, add the new repo and pull info from the repo.
  • [RESULT] error message index signature mismatch