Beta v0.2.0

A new fix is out! OldWorldFix v0.2.0-beta fixes an important issue with old maps:

• Custom potion spawners don't break in 1.11-1.12
• Custom potion spawners don't cause chunk errors in 1.13+!

NOTE:
Since custom spawners are much more complicated (and used much less) than simple chests and potions, this feature is hard to test alone. Please be careful and if converting a world you care about, backup. Please, if you encounter any problems, let me know by posting an issue.

Beta v0.1.0

The first public release! OldWorldFix v0.1.0-beta introduces two very important fixes for old worlds:

• Invalid chests don't disappear (Problem since Minecraft 1.8)
• Potions don't turn into water bottles (Problem since Minecraft 1.13)

IMPORTANT NOTE: You should back up your world before you use this. While I had no problems testing it, your mileage may vary.
ABOUT POTION FIXES: The potion fix is only necessary when converting a pre-1.9 world to 1.13+. If you apply the fix, potions will be fixed in 1.13+ but will be broken in 1.8 and earlier. Be careful with this.

If you do have any problems, please submit an issue and I will see what I can do to fix it. If you have any suggestions, those are free to go into issues as well.