diff --git a/src/main/java/com/github/zly2006/reden/Reden.kt b/src/main/java/com/github/zly2006/reden/Reden.kt
index ac351396..05c6ce75 100644
--- a/src/main/java/com/github/zly2006/reden/Reden.kt
+++ b/src/main/java/com/github/zly2006/reden/Reden.kt
@@ -9,6 +9,7 @@ import com.github.zly2006.reden.carpet.RedenCarpetSettings
 import com.github.zly2006.reden.indexing.blockId
 import com.github.zly2006.reden.indexing.entityId
 import com.github.zly2006.reden.indexing.propertyId
+import com.github.zly2006.reden.mixinhelper.UpdateMonitorHelper
 import com.github.zly2006.reden.network.registerChannels
 import com.github.zly2006.reden.rvc.registerRvc
 import com.github.zly2006.reden.transformers.ThisIsReden
@@ -82,7 +83,10 @@ class Reden : ModInitializer, CarpetExtension {
 
     @OptIn(DelicateCoroutinesApi::class)
     override fun onInitialize() {
-        ServerLifecycleEvents.SERVER_STARTING.register { server = it }
+        ServerLifecycleEvents.SERVER_STARTING.register {
+            UpdateMonitorHelper.cleanup()
+            server = it
+        }
         registerChannels()
         CarpetServer.manageExtension(this)
         CommandRegistrationCallback.EVENT.register { dispatcher, access, _ ->
diff --git a/src/main/java/com/github/zly2006/reden/mixinhelper/UpdateMonitorHelper.kt b/src/main/java/com/github/zly2006/reden/mixinhelper/UpdateMonitorHelper.kt
index 0701fcfd..1b4a1d01 100644
--- a/src/main/java/com/github/zly2006/reden/mixinhelper/UpdateMonitorHelper.kt
+++ b/src/main/java/com/github/zly2006/reden/mixinhelper/UpdateMonitorHelper.kt
@@ -21,7 +21,6 @@ import com.github.zly2006.reden.mixinhelper.UpdateMonitorHelper.undoRecordsMap
 import com.github.zly2006.reden.utils.debugLogger
 import com.github.zly2006.reden.utils.isClient
 import com.github.zly2006.reden.utils.server
-import net.fabricmc.fabric.api.event.lifecycle.v1.ServerTickEvents
 import net.fabricmc.fabric.api.networking.v1.ServerPlayConnectionEvents
 import net.minecraft.block.BlockState
 import net.minecraft.entity.Entity
@@ -88,6 +87,14 @@ object UpdateMonitorHelper {
     val undoRecordsMap: MutableMap<Long, PlayerData.UndoRecord> = HashMap()
     internal val undoRecords = mutableListOf<UndoRecordEntry>()
 
+    /**
+     * Used for crash recovery.
+     */
+    fun cleanup() {
+        undoRecordsMap.clear()
+        undoRecords.clear()
+    }
+
     private fun filterLogById(undoId: Long) =
         undoId != 0L || if (isClient) !DEBUG_LOGGER_IGNORE_UNDO_ID_0.booleanValue else true
 
@@ -114,12 +121,6 @@ object UpdateMonitorHelper {
         }
         return undoRecords.removeLast()
     }
-    data class Changed(
-        val record: PlayerData.UndoRecord,
-        val pos: BlockPos
-    )
-    var lastTickChanged: MutableSet<Changed> = hashSetOf(); private set
-    var thisTickChanged: MutableSet<Changed> = hashSetOf(); private set
     val recording: PlayerData.UndoRecord? get() = undoRecords.lastOrNull()?.record
 
     /**
@@ -297,9 +298,5 @@ object UpdateMonitorHelper {
 
     init {
         ServerPlayConnectionEvents.DISCONNECT.register { handler, _ -> playerQuit(handler.player) }
-        ServerTickEvents.START_SERVER_TICK.register {
-            lastTickChanged = thisTickChanged
-            thisTickChanged = hashSetOf()
-        }
     }
 }