Jungle Saplings dropping as Oak Saplings

Please provide some image examples and steps to reproduce as I am not aware on how you encountered this.

Keep in mind that oak leaves generate in clusters around a single jungle log in jungle biomes. These leaves will of course drop oak saplings rather than jungle saplings.

Yes; make sure that they are actually jungle leaves and not oak leaves.

Thank you for your report!
We're tracking this issue in MC-156133, so this ticket is being resolved and linked as a duplicate.

That ticket has already been resolved as working as intended, which means this is not considered a bug and won't be fixed. Please do not leave a comment on the linked ticket.

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