[MC-310729] Explorer maps from previous versions prevent saved hotbars from loading

If you have Old Explorer Maps saved inside your Saved Hotbar, the entire Saved Hotbar will not load in the most recent snapshot.

Linked issues

is duplicated by 2

MC-310708 Saved toolbars throwing an error Resolved

MC-310877 Can't Open World Resolved

Attachments

Comments 3

Automation for Jira 2026-08-04T22:14:16Z

Thank you for helping us improve Minecraft! We saved your files:

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tryashtar 2026-08-05T00:17:09Z

Confirmed, this also logs the following error:

[18:13:09] [Render thread] [ERROR] java.lang.IllegalStateException: Could not create default value for type: NamedType["item_name", NamespacedString]
        at com.mojang.datafixers.Typed.lambda$getOrCreate$1(Typed.java:74)
        at java.base/java.util.Optional.orElseThrow(Optional.java:407)
        at com.mojang.datafixers.Typed.getOrCreate(Typed.java:74)
        at net.minecraft.util.datafix.fixes.ExplorerMapItemFix.lambda$makeRule$0(ExplorerMapItemFix.java:84)
        at com.mojang.datafixers.DataFix.lambda$checked$3(DataFix.java:98)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166)
        at com.mojang.datafixers.util.Either$Right.map(Either.java:99)
        at com.mojang.datafixers.util.Either.mapRight(Either.java:166)
        at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166)
        at com.mojang.datafixers.util.Either$Right.map(Either.java:99)
        at com.mojang.datafixers.util.Either.mapRight(Either.java:166)
        at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166)
        at com.mojang.datafixers.util.Either$Right.map(Either.java:99)
        at com.mojang.datafixers.util.Either.mapRight(Either.java:166)
        at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166)
        at com.mojang.datafixers.util.Either$Right.map(Either.java:99)
        at com.mojang.datafixers.util.Either.mapRight(Either.java:166)
        at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166)
        at com.mojang.datafixers.util.Either$Right.map(Either.java:99)
        at com.mojang.datafixers.util.Either.mapRight(Either.java:166)
        at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166)
        at com.mojang.datafixers.util.Either$Right.map(Either.java:99)
        at com.mojang.datafixers.util.Either.mapRight(Either.java:166)
        at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166)
        at com.mojang.datafixers.util.Either$Right.map(Either.java:99)
        at com.mojang.datafixers.util.Either.mapRight(Either.java:166)
        at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.functions.Comp.applyUnchecked(Comp.java:126)
        at com.mojang.datafixers.functions.Comp.lambda$eval$2(Comp.java:118)
        at com.mojang.datafixers.functions.Fold.lambda$eval$2(Fold.java:91)
        at com.mojang.datafixers.functions.Comp.applyUnchecked(Comp.java:126)
        at com.mojang.datafixers.functions.Comp.lambda$eval$2(Comp.java:118)
        at com.mojang.datafixers.FunctionType$Instance.lambda$wander$3(FunctionType.java:93)
        at com.mojang.datafixers.optics.ListTraversal.lambda$wander$0(ListTraversal.java:24)
        at com.mojang.datafixers.FunctionType$Instance.lambda$wander$4(FunctionType.java:94)
        at com.mojang.datafixers.FunctionType$Instance.lambda$first$1(FunctionType.java:81)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.FunctionType$Instance.lambda$wander$3(FunctionType.java:93)
        at com.mojang.datafixers.optics.ListTraversal.lambda$wander$0(ListTraversal.java:24)
        at com.mojang.datafixers.FunctionType$Instance.lambda$wander$4(FunctionType.java:94)
        at com.mojang.datafixers.FunctionType$Instance.lambda$first$1(FunctionType.java:81)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.FunctionType$Instance.lambda$first$1(FunctionType.java:81)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at java.base/java.util.function.Function.lambda$compose$0(Function.java:68)
        at com.mojang.datafixers.types.Type.capWrite(Type.java:167)
        at com.mojang.datafixers.types.Type.lambda$readAndWrite$10(Type.java:159)
        at com.mojang.serialization.DataResult$Error.flatMap(DataResult.java:335)
        at com.mojang.serialization.DataResult$Error.flatMap(DataResult.java:250)
        at com.mojang.datafixers.types.Type.readAndWrite(Type.java:158)
        at com.mojang.datafixers.DataFixerUpper.update(DataFixerUpper.java:78)
        at net.minecraft.util.datafix.DataFixTypes.update(DataFixTypes.java:87)
        at net.minecraft.util.datafix.DataFixTypes.update(DataFixTypes.java:95)
        at net.minecraft.util.datafix.DataFixTypes.updateToCurrentVersion(DataFixTypes.java:99)
        at net.minecraft.client.HotbarManager.load(HotbarManager.java:44)
        at net.minecraft.client.HotbarManager.get(HotbarManager.java:72)
        at net.minecraft.client.gui.screens.inventory.CreativeModeInventoryScreen.handleHotbarLoadOrSave(CreativeModeInventoryScreen.java:1060)
        at net.minecraft.client.Minecraft.handleKeybinds(Minecraft.java:2008)
        at net.minecraft.client.Minecraft.tick(Minecraft.java:1897)
        at net.minecraft.client.Minecraft.runTick(Minecraft.java:1246)
        at net.minecraft.client.Minecraft.run(Minecraft.java:958)
        at net.minecraft.client.main.Main.main(Main.java:292)

[Mojang] Triage Team 2026-08-05T07:53:30Z

This issue has been reviewed by our team.

Please add new, relevant information if it helps us understand or reproduce the issue. To show that you’re affected, use the vote feature rather than commenting.

If a fix is implemented, it will be listed in our official changelogs.

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