diff --git a/buildSrc/src/main/kotlin/Versions.kt b/buildSrc/src/main/kotlin/Versions.kt
index 4ccb5ffc..eed844a2 100644
--- a/buildSrc/src/main/kotlin/Versions.kt
+++ b/buildSrc/src/main/kotlin/Versions.kt
@@ -7,7 +7,7 @@ object Versions {
     const val guava = "17.0"
     const val fabricLoader = "0.4.8+build.154"
     const val log4j = "2.8.1"
-    const val jetbrainsAnnotations = "20.1.0"
+    const val checkerQual = "3.12.0"
 
     // Platforms
     const val spigot = "1.16.5-R0.1-SNAPSHOT"
diff --git a/common/build.gradle.kts b/common/build.gradle.kts
index 17131050..49375bfc 100644
--- a/common/build.gradle.kts
+++ b/common/build.gradle.kts
@@ -11,5 +11,5 @@ dependencies {
     compileOnly("io.netty", "netty-all", Versions.netty)
     compileOnlyApi("us.myles", "viaversion", Versions.viaversion)
     compileOnlyApi("com.google.guava", "guava", Versions.guava)
-    compileOnlyApi("org.jetbrains", "annotations", Versions.jetbrainsAnnotations)
+    compileOnlyApi("org.checkerframework", "checker-qual", Versions.checkerQual)
 }
\ No newline at end of file
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/BackwardsProtocol.java b/common/src/main/java/nl/matsv/viabackwards/api/BackwardsProtocol.java
index a32cc25d..32cee59a 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/BackwardsProtocol.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/BackwardsProtocol.java
@@ -19,7 +19,7 @@ package nl.matsv.viabackwards.api;
 
 import nl.matsv.viabackwards.api.data.BackwardsMappings;
 import nl.matsv.viabackwards.api.entities.storage.EntityTracker;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.UserConnection;
 import us.myles.ViaVersion.api.protocol.ClientboundPacketType;
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/data/BackwardsMappings.java b/common/src/main/java/nl/matsv/viabackwards/api/data/BackwardsMappings.java
index c6445e28..bec56b31 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/data/BackwardsMappings.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/data/BackwardsMappings.java
@@ -19,7 +19,7 @@ package nl.matsv.viabackwards.api.data;
 
 import com.google.common.base.Preconditions;
 import nl.matsv.viabackwards.api.BackwardsProtocol;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.MappingData;
 import us.myles.ViaVersion.api.data.Mappings;
@@ -71,8 +71,7 @@ public class BackwardsMappings extends MappingData {
     }
 
     @Override
-    @Nullable
-    protected Mappings loadFromArray(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
+    protected @Nullable Mappings loadFromArray(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
         if (!oldMappings.has(key) || !newMappings.has(key)) return null;
 
         JsonObject diff = diffMappings != null ? diffMappings.getAsJsonObject(key) : null;
@@ -80,8 +79,7 @@ public class BackwardsMappings extends MappingData {
     }
 
     @Override
-    @Nullable
-    protected Mappings loadFromObject(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
+    protected @Nullable Mappings loadFromObject(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
         if (!oldMappings.has(key) || !newMappings.has(key)) return null;
 
         JsonObject diff = diffMappings != null ? diffMappings.getAsJsonObject(key) : null;
@@ -124,13 +122,11 @@ public class BackwardsMappings extends MappingData {
         return checkValidity(id, this.itemMappings.inverse().get(id), "item");
     }
 
-    @Nullable
-    public MappedItem getMappedItem(int id) {
+    public @Nullable MappedItem getMappedItem(int id) {
         return backwardsItemMappings != null ? backwardsItemMappings.get(id) : null;
     }
 
-    @Nullable
-    public String getMappedNamedSound(String id) {
+    public @Nullable String getMappedNamedSound(String id) {
         if (backwardsItemMappings == null) {
             return null;
         }
@@ -142,13 +138,11 @@ public class BackwardsMappings extends MappingData {
         return backwardsSoundMappings.get(id);
     }
 
-    @Nullable
-    public Int2ObjectMap<MappedItem> getBackwardsItemMappings() {
+    public @Nullable Int2ObjectMap<MappedItem> getBackwardsItemMappings() {
         return backwardsItemMappings;
     }
 
-    @Nullable
-    public Map<String, String> getBackwardsSoundMappings() {
+    public @Nullable Map<String, String> getBackwardsSoundMappings() {
         return backwardsSoundMappings;
     }
 }
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/data/MappedLegacyBlockItem.java b/common/src/main/java/nl/matsv/viabackwards/api/data/MappedLegacyBlockItem.java
index dc5c8225..40ab4454 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/data/MappedLegacyBlockItem.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/data/MappedLegacyBlockItem.java
@@ -18,7 +18,7 @@
 package nl.matsv.viabackwards.api.data;
 
 import nl.matsv.viabackwards.utils.Block;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.viaversion.libs.opennbt.tag.builtin.CompoundTag;
 
 public class MappedLegacyBlockItem {
@@ -60,8 +60,7 @@ public class MappedLegacyBlockItem {
         return blockEntityHandler != null;
     }
 
-    @Nullable
-    public BlockEntityHandler getBlockEntityHandler() {
+    public @Nullable BlockEntityHandler getBlockEntityHandler() {
         return blockEntityHandler;
     }
 
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/entities/meta/MetaHandlerEvent.java b/common/src/main/java/nl/matsv/viabackwards/api/entities/meta/MetaHandlerEvent.java
index 3f8c737b..af686c9f 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/entities/meta/MetaHandlerEvent.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/entities/meta/MetaHandlerEvent.java
@@ -20,7 +20,7 @@ package nl.matsv.viabackwards.api.entities.meta;
 
 import nl.matsv.viabackwards.api.entities.storage.EntityTracker;
 import nl.matsv.viabackwards.api.entities.storage.MetaStorage;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.data.UserConnection;
 import us.myles.ViaVersion.api.minecraft.metadata.Metadata;
 
@@ -87,8 +87,7 @@ public class MetaHandlerEvent {
     /**
      * May be null, use {@link #createMeta(Metadata)} for adding metadata.
      */
-    @Nullable
-    public List<Metadata> getExtraData() {
+    public @Nullable List<Metadata> getExtraData() {
         return extraData;
     }
 }
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/entities/meta/MetaHandlerSettings.java b/common/src/main/java/nl/matsv/viabackwards/api/entities/meta/MetaHandlerSettings.java
index cbdd36e3..26308a99 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/entities/meta/MetaHandlerSettings.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/entities/meta/MetaHandlerSettings.java
@@ -19,7 +19,7 @@
 package nl.matsv.viabackwards.api.entities.meta;
 
 import nl.matsv.viabackwards.api.exceptions.RemovedValueException;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.entities.EntityType;
 import us.myles.ViaVersion.api.minecraft.metadata.Metadata;
 
@@ -109,8 +109,7 @@ public class MetaHandlerSettings {
         return filterIndex;
     }
 
-    @Nullable
-    public MetaHandler getHandler() {
+    public @Nullable MetaHandler getHandler() {
         return handler;
     }
 
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/EntityData.java b/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/EntityData.java
index 5f3f9b38..0e2d8daa 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/EntityData.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/EntityData.java
@@ -18,7 +18,7 @@
 
 package nl.matsv.viabackwards.api.entities.storage;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.protocols.protocol1_13to1_12_2.ChatRewriter;
 
 public class EntityData {
@@ -58,8 +58,7 @@ public class EntityData {
     /**
      * @return custom mobname, can be either a String or a JsonElement
      */
-    @Nullable
-    public Object getMobName() {
+    public @Nullable Object getMobName() {
         return mobName;
     }
 
@@ -67,8 +66,7 @@ public class EntityData {
         return replacementId;
     }
 
-    @Nullable
-    public MetaCreator getDefaultMeta() {
+    public @Nullable MetaCreator getDefaultMeta() {
         return defaultMeta;
     }
 
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/EntityTracker.java b/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/EntityTracker.java
index 201678c9..ab2c1f3d 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/EntityTracker.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/EntityTracker.java
@@ -19,7 +19,7 @@
 package nl.matsv.viabackwards.api.entities.storage;
 
 import nl.matsv.viabackwards.api.BackwardsProtocol;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.data.StoredObject;
 import us.myles.ViaVersion.api.data.UserConnection;
 import us.myles.ViaVersion.api.entities.EntityType;
@@ -41,8 +41,7 @@ public class EntityTracker extends StoredObject {
         trackers.put(protocol, new ProtocolEntityTracker());
     }
 
-    @Nullable
-    public ProtocolEntityTracker get(BackwardsProtocol protocol) {
+    public @Nullable ProtocolEntityTracker get(BackwardsProtocol protocol) {
         return trackers.get(protocol);
     }
 
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/MetaStorage.java b/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/MetaStorage.java
index bc8146fa..bb5b3fab 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/MetaStorage.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/entities/storage/MetaStorage.java
@@ -18,7 +18,7 @@
 
 package nl.matsv.viabackwards.api.entities.storage;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.minecraft.metadata.Metadata;
 
 import java.util.List;
@@ -46,8 +46,7 @@ public class MetaStorage {
         this.metaDataList.add(data);
     }
 
-    @Nullable
-    public Metadata get(int index) {
+    public @Nullable Metadata get(int index) {
         for (Metadata meta : this.metaDataList) {
             if (index == meta.getId()) {
                 return meta;
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/rewriters/EntityRewriterBase.java b/common/src/main/java/nl/matsv/viabackwards/api/rewriters/EntityRewriterBase.java
index 0d3394e1..f5348571 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/rewriters/EntityRewriterBase.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/rewriters/EntityRewriterBase.java
@@ -26,7 +26,7 @@ import nl.matsv.viabackwards.api.entities.storage.EntityData;
 import nl.matsv.viabackwards.api.entities.storage.EntityTracker;
 import nl.matsv.viabackwards.api.entities.storage.MetaStorage;
 import nl.matsv.viabackwards.api.exceptions.RemovedValueException;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.PacketWrapper;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.ParticleMappings;
@@ -91,8 +91,7 @@ public abstract class EntityRewriterBase<T extends BackwardsProtocol> extends Re
         return entityTypes.containsKey(type);
     }
 
-    @Nullable
-    protected EntityData getEntityData(EntityType type) {
+    protected @Nullable EntityData getEntityData(EntityType type) {
         return entityTypes.get(type);
     }
 
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/rewriters/ItemRewriter.java b/common/src/main/java/nl/matsv/viabackwards/api/rewriters/ItemRewriter.java
index 8b2d6702..86a336b9 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/rewriters/ItemRewriter.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/rewriters/ItemRewriter.java
@@ -19,7 +19,7 @@ package nl.matsv.viabackwards.api.rewriters;
 
 import nl.matsv.viabackwards.api.BackwardsProtocol;
 import nl.matsv.viabackwards.api.data.MappedItem;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.minecraft.item.Item;
 import us.myles.viaversion.libs.opennbt.tag.builtin.ByteTag;
 import us.myles.viaversion.libs.opennbt.tag.builtin.CompoundTag;
@@ -38,8 +38,7 @@ public abstract class ItemRewriter<T extends BackwardsProtocol> extends ItemRewr
     }
 
     @Override
-    @Nullable
-    public Item handleItemToClient(Item item) {
+    public @Nullable Item handleItemToClient(Item item) {
         if (item == null) return null;
 
         CompoundTag display = item.getTag() != null ? item.getTag().get("display") : null;
@@ -100,8 +99,7 @@ public abstract class ItemRewriter<T extends BackwardsProtocol> extends ItemRewr
     }
 
     @Override
-    @Nullable
-    public Item handleItemToServer(Item item) {
+    public @Nullable Item handleItemToServer(Item item) {
         if (item == null) return null;
 
         super.handleItemToServer(item);
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/rewriters/ItemRewriterBase.java b/common/src/main/java/nl/matsv/viabackwards/api/rewriters/ItemRewriterBase.java
index bf2ae4ab..c0621076 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/rewriters/ItemRewriterBase.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/rewriters/ItemRewriterBase.java
@@ -18,7 +18,7 @@
 package nl.matsv.viabackwards.api.rewriters;
 
 import nl.matsv.viabackwards.api.BackwardsProtocol;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.minecraft.item.Item;
 import us.myles.viaversion.libs.opennbt.tag.builtin.CompoundTag;
 import us.myles.viaversion.libs.opennbt.tag.builtin.ListTag;
@@ -36,8 +36,7 @@ public abstract class ItemRewriterBase<T extends BackwardsProtocol> extends Rewr
         nbtTagName = "VB|" + protocol.getClass().getSimpleName();
     }
 
-    @Nullable
-    public Item handleItemToClient(Item item) {
+    public @Nullable Item handleItemToClient(Item item) {
         if (item == null) return null;
         if (protocol.getMappingData() != null && protocol.getMappingData().getItemMappings() != null) {
             item.setIdentifier(protocol.getMappingData().getNewItemId(item.getIdentifier()));
@@ -45,8 +44,7 @@ public abstract class ItemRewriterBase<T extends BackwardsProtocol> extends Rewr
         return item;
     }
 
-    @Nullable
-    public Item handleItemToServer(Item item) {
+    public @Nullable Item handleItemToServer(Item item) {
         if (item == null) return null;
         if (protocol.getMappingData() != null && protocol.getMappingData().getItemMappings() != null) {
             item.setIdentifier(protocol.getMappingData().getOldItemId(item.getIdentifier()));
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/rewriters/LegacyBlockItemRewriter.java b/common/src/main/java/nl/matsv/viabackwards/api/rewriters/LegacyBlockItemRewriter.java
index be45f337..2c659bbb 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/rewriters/LegacyBlockItemRewriter.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/rewriters/LegacyBlockItemRewriter.java
@@ -23,7 +23,7 @@ import nl.matsv.viabackwards.api.data.MappedLegacyBlockItem;
 import nl.matsv.viabackwards.api.data.VBMappingDataLoader;
 import nl.matsv.viabackwards.protocol.protocol1_11_1to1_12.data.BlockColors;
 import nl.matsv.viabackwards.utils.Block;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.minecraft.chunks.Chunk;
 import us.myles.ViaVersion.api.minecraft.chunks.ChunkSection;
 import us.myles.ViaVersion.api.minecraft.item.Item;
@@ -92,8 +92,7 @@ public abstract class LegacyBlockItemRewriter<T extends BackwardsProtocol> exten
     }
 
     @Override
-    @Nullable
-    public Item handleItemToClient(Item item) {
+    public @Nullable Item handleItemToClient(Item item) {
         if (item == null) return null;
 
         MappedLegacyBlockItem data = replacementData.get(item.getIdentifier());
@@ -145,8 +144,7 @@ public abstract class LegacyBlockItemRewriter<T extends BackwardsProtocol> exten
         return (b.getId() << 4 | (b.getData() & 15));
     }
 
-    @Nullable
-    public Block handleBlock(int blockId, int data) {
+    public @Nullable Block handleBlock(int blockId, int data) {
         MappedLegacyBlockItem settings = replacementData.get(blockId);
         if (settings == null || !settings.isBlock()) return null;
 
diff --git a/common/src/main/java/nl/matsv/viabackwards/api/rewriters/LegacyEntityRewriter.java b/common/src/main/java/nl/matsv/viabackwards/api/rewriters/LegacyEntityRewriter.java
index 7407c4f8..787a8bc5 100644
--- a/common/src/main/java/nl/matsv/viabackwards/api/rewriters/LegacyEntityRewriter.java
+++ b/common/src/main/java/nl/matsv/viabackwards/api/rewriters/LegacyEntityRewriter.java
@@ -22,7 +22,7 @@ import nl.matsv.viabackwards.api.BackwardsProtocol;
 import nl.matsv.viabackwards.api.entities.storage.EntityData;
 import nl.matsv.viabackwards.api.entities.storage.EntityObjectData;
 import nl.matsv.viabackwards.api.entities.storage.MetaStorage;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.entities.EntityType;
 import us.myles.ViaVersion.api.entities.ObjectType;
 import us.myles.ViaVersion.api.minecraft.metadata.MetaType;
@@ -56,8 +56,7 @@ public abstract class LegacyEntityRewriter<T extends BackwardsProtocol> extends
         return entData;
     }
 
-    @Nullable
-    protected EntityData getObjectData(ObjectType type) {
+    protected @Nullable EntityData getObjectData(ObjectType type) {
         return objectTypes.get(type);
     }
 
diff --git a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_11_1to1_12/packets/BlockItemPackets1_12.java b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_11_1to1_12/packets/BlockItemPackets1_12.java
index 6a77e8de..6cd0637c 100644
--- a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_11_1to1_12/packets/BlockItemPackets1_12.java
+++ b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_11_1to1_12/packets/BlockItemPackets1_12.java
@@ -21,7 +21,7 @@ package nl.matsv.viabackwards.protocol.protocol1_11_1to1_12.packets;
 import nl.matsv.viabackwards.api.rewriters.LegacyBlockItemRewriter;
 import nl.matsv.viabackwards.protocol.protocol1_11_1to1_12.Protocol1_11_1To1_12;
 import nl.matsv.viabackwards.protocol.protocol1_11_1to1_12.data.MapColorMapping;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.PacketWrapper;
 import us.myles.ViaVersion.api.minecraft.BlockChangeRecord;
 import us.myles.ViaVersion.api.minecraft.chunks.Chunk;
diff --git a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_12_2to1_13/data/BackwardsMappings.java b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_12_2to1_13/data/BackwardsMappings.java
index 5708190b..211f7e03 100644
--- a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_12_2to1_13/data/BackwardsMappings.java
+++ b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_12_2to1_13/data/BackwardsMappings.java
@@ -20,7 +20,7 @@ package nl.matsv.viabackwards.protocol.protocol1_12_2to1_13.data;
 
 import nl.matsv.viabackwards.ViaBackwards;
 import nl.matsv.viabackwards.api.data.VBMappings;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.MappingDataLoader;
 import us.myles.ViaVersion.api.data.Mappings;
@@ -95,8 +95,7 @@ public class BackwardsMappings extends nl.matsv.viabackwards.api.data.BackwardsM
     }
 
     @Override
-    @Nullable
-    protected Mappings loadFromObject(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
+    protected @Nullable Mappings loadFromObject(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
         if (key.equals("blockstates")) {
             short[] oldToNew = new short[8582];
             Arrays.fill(oldToNew, (short) -1);
diff --git a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_13_2to1_14/data/CommandRewriter1_14.java b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_13_2to1_14/data/CommandRewriter1_14.java
index 2a0cf19e..75e615ec 100644
--- a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_13_2to1_14/data/CommandRewriter1_14.java
+++ b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_13_2to1_14/data/CommandRewriter1_14.java
@@ -17,7 +17,7 @@
  */
 package nl.matsv.viabackwards.protocol.protocol1_13_2to1_14.data;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.protocol.Protocol;
 import us.myles.ViaVersion.api.rewriters.CommandRewriter;
 import us.myles.ViaVersion.api.type.Type;
@@ -37,8 +37,7 @@ public class CommandRewriter1_14 extends CommandRewriter {
     }
 
     @Override
-    @Nullable
-    protected String handleArgumentType(String argumentType) {
+    protected @Nullable String handleArgumentType(String argumentType) {
         switch (argumentType) {
             case "minecraft:nbt_compound_tag":
                 return "minecraft:nbt";
diff --git a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_13to1_13_1/data/CommandRewriter1_13_1.java b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_13to1_13_1/data/CommandRewriter1_13_1.java
index 6e98482f..c33e943a 100644
--- a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_13to1_13_1/data/CommandRewriter1_13_1.java
+++ b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_13to1_13_1/data/CommandRewriter1_13_1.java
@@ -17,7 +17,7 @@
  */
 package nl.matsv.viabackwards.protocol.protocol1_13to1_13_1.data;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.protocol.Protocol;
 import us.myles.ViaVersion.api.rewriters.CommandRewriter;
 import us.myles.ViaVersion.api.type.Type;
@@ -33,8 +33,7 @@ public class CommandRewriter1_13_1 extends CommandRewriter {
     }
 
     @Override
-    @Nullable
-    protected String handleArgumentType(String argumentType) {
+    protected @Nullable String handleArgumentType(String argumentType) {
         if (argumentType.equals("minecraft:column_pos")) {
             return "minecraft:vec2";
         } else if (argumentType.equals("minecraft:dimension")) {
diff --git a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_15_2to1_16/data/CommandRewriter1_16.java b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_15_2to1_16/data/CommandRewriter1_16.java
index 62c8fcd3..6bb82257 100644
--- a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_15_2to1_16/data/CommandRewriter1_16.java
+++ b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_15_2to1_16/data/CommandRewriter1_16.java
@@ -17,7 +17,7 @@
  */
 package nl.matsv.viabackwards.protocol.protocol1_15_2to1_16.data;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.protocol.Protocol;
 import us.myles.ViaVersion.api.rewriters.CommandRewriter;
 
@@ -28,8 +28,7 @@ public class CommandRewriter1_16 extends CommandRewriter {
     }
 
     @Override
-    @Nullable
-    protected String handleArgumentType(String argumentType) {
+    protected @Nullable String handleArgumentType(String argumentType) {
         if (argumentType.equals("minecraft:uuid")) {
             return "minecraft:game_profile";
         }
diff --git a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_16_1to1_16_2/data/CommandRewriter1_16_2.java b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_16_1to1_16_2/data/CommandRewriter1_16_2.java
index 769dc5cf..1d3860ae 100644
--- a/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_16_1to1_16_2/data/CommandRewriter1_16_2.java
+++ b/common/src/main/java/nl/matsv/viabackwards/protocol/protocol1_16_1to1_16_2/data/CommandRewriter1_16_2.java
@@ -17,7 +17,7 @@
  */
 package nl.matsv.viabackwards.protocol.protocol1_16_1to1_16_2.data;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.protocol.Protocol;
 import us.myles.ViaVersion.api.rewriters.CommandRewriter;
 import us.myles.ViaVersion.api.type.Type;
@@ -33,8 +33,7 @@ public class CommandRewriter1_16_2 extends CommandRewriter {
     }
 
     @Override
-    @Nullable
-    protected String handleArgumentType(String argumentType) {
+    protected @Nullable String handleArgumentType(String argumentType) {
         if (argumentType.equals("minecraft:angle")) {
             return "brigadier:string";
         }