diff --git a/modules/events-mod/src/main/typescript/main/events/onMapChunkEventListeners.ts b/modules/events-mod/src/main/typescript/main/events/onMapChunkEventListeners.ts
index 84fdad3..e30886d 100644
--- a/modules/events-mod/src/main/typescript/main/events/onMapChunkEventListeners.ts
+++ b/modules/events-mod/src/main/typescript/main/events/onMapChunkEventListeners.ts
@@ -3,8 +3,7 @@ import {Converters} from "./converters";
 import EventUpdatesManager, {EventUpdates} from "../cache/EventDataCache";
 import {
   KafkatorioPacketData,
-  MapChunkPosition,
-  MapTileDictionary
+  MapChunkPosition
 } from "../../generated/kafkatorio-schema/kafkatorio-schema";
 import CacheKey = EventUpdates.PacketKey;
 import Type = KafkatorioPacketData.Type;
@@ -13,18 +12,6 @@ import Type = KafkatorioPacketData.Type;
 type MapChunkUpdater = (data: KafkatorioPacketData.MapChunkUpdate) => void
 
 
-const mapProtoNameToKey: { [key: string]: uint } = {}
-let protoIndex: uint = 0
-
-
-function getProtoKey(protoName: string): uint {
-  if (mapProtoNameToKey[protoName] == undefined) {
-    mapProtoNameToKey[protoName] = protoIndex++
-  }
-  return mapProtoNameToKey[protoName]
-}
-
-
 function mapTilesUpdateDebounce(
     surface: LuaSurface | undefined,
     chunkPosition: MapChunkPosition,
@@ -47,27 +34,31 @@ function mapTilesUpdateDebounce(
       key,
       Type.MapChunkUpdate,
       data => {
-        data.tileDictionary ??= <MapTileDictionary>{
+
+        // tile dictionary update
+        data.tileDictionary ??= {
           tilesXY: {},
           protos: {},
         }
 
+        let protosCount: uint = 0
         for (const tile of tiles) {
+          data.tileDictionary.protos[tile.name] ??= protosCount++
+          const protoKey = data.tileDictionary.protos[tile.name]
 
           const xString = `${tile.position.x}`
           const yString = `${tile.position.y}`
-          const protoKey = getProtoKey(tile.name)
-
-          data.tileDictionary.protos[tile.name] = protoIndex
 
           data.tileDictionary.tilesXY[xString] ??= {}
           data.tileDictionary.tilesXY[xString][yString] = protoKey
         }
 
+        // events count update
         data.eventCounts ??= {}
         data.eventCounts[eventName] ??= 0
         data.eventCounts[eventName]++
 
+        // apply mutator
         if (updater != undefined) {
           updater(data)
         }
diff --git a/modules/events-schema/src/commonMain/kotlin/dev/adamko/kafkatorio/schema/common/mapTile.kt b/modules/events-schema/src/commonMain/kotlin/dev/adamko/kafkatorio/schema/common/mapTile.kt
index 7073785..ef2ec02 100644
--- a/modules/events-schema/src/commonMain/kotlin/dev/adamko/kafkatorio/schema/common/mapTile.kt
+++ b/modules/events-schema/src/commonMain/kotlin/dev/adamko/kafkatorio/schema/common/mapTile.kt
@@ -50,15 +50,17 @@ data class MapTileDictionary(
         val protoName = protosIndexToName[protoIndex]
         if (x != null && y != null && protoName != null) {
           add(MapTile(x, y, protoName))
+        } else if (protoName == null) {
+          println("warning: no prototype name found for index:$protoIndex. $protosIndexToName")
         }
       }
     }
   }
 
-  /** The collection-index of a prototype in [MapTileDictionary.protos] */
+  /** An arbitrary ID for a prototype in [MapTileDictionary.protos]. */
   @Serializable
   @JvmInline
-  value class PrototypeKey(val index: Int)
+  value class PrototypeKey(private val index: Int)
 
   companion object {
     fun MapTileDictionary?.isNullOrEmpty(): Boolean {