Custom Biomes are reset after upgrading from 1.17 to 1.18

When upgrading a world from 1.17.1 to 1.18, dimensions that had custom biomes reset to a default biome, I had recently upgraded a world that had a custom dimension datapack installed. It worked completely fine in 1.17.1. However, when upgrading to 1.18, the custom dimension's custom biomes seem to reset and not carry over.