[MC-185375] Wither Skeletons not spawning in 20w21a

I started a new world in the snapshots of the 1.16 Update, don't know which one exactly but now I have updated to 20w21a and I have just noticed that the nether fortresses don't seem to be spawning wither skeletons anymore, I think that in previous snapshots they were spawning

Linked issues

duplicates 1

MC-184740 Structures generated in previous versions are not recognised as valid structures, causing mobs not to spawn Resolved

Comments 2

galaxy_2alex 2020-05-23T21:34:38Z

Thank you for your report!
However, this issue is a Duplicate of MC-184740.

Please use the search function in the future to prevent duplicate reports.

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migrated 2020-05-23T21:35:21Z

I just created a new world and they are spawning in the new one just fine, how can I make them spawn in my other world too, I don't wanna lose all my progress