Trouble with Heroku buildpacks and stacks

Hello! We’re trying to port a Heroku ruby app over to Render but running into a stack related issue.

On Heroku we use the heroku-20 stack (not 22). We’re specifying 20 in our Dockerfile.render (ARG HEROKU_STACK=v2-heroku-20), our app.json specifies heroku-20 as the stack, and we’ve set a STACK environment variable in Render for good measure.

During the build process, our buildpacks are properly extracted as 20 (#5 [builder 1/1] FROM but when Render tries to build it’s using the heroku 22 stack (#9 [builder 3/1] RUN /render/build-scripts/ heroku-22).

How can we get that /render/build-scripts/ script to use heroku-20?

thanks very much!

Hey Seann,
We made some changes to the importer on Friday specifically around stacks so it might be worth checking the plugin is up to date ( heroku update should be enough and run the import again just to check if any of the generated files get updated. It not, can you share your serviceID and we can take a look at what’s going on here.

John B

Hey John B,

I’d just like to throw a quick +1 on this question. I installed the Heroku importer plugin today, ran it to try test things, and am hitting exactly the same problem described in the original question above.

Thanks for your help!


Hey Seann,

I managed to fix this problem by adding a new environment variable:


Hope this helps - cheerio!


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