diff --git a/ui-ngx/src/app/shared/models/widget/maps/map-model.definition.ts b/ui-ngx/src/app/shared/models/widget/maps/map-model.definition.ts
index 681722c0c3..94eced7fcf 100644
--- a/ui-ngx/src/app/shared/models/widget/maps/map-model.definition.ts
+++ b/ui-ngx/src/app/shared/models/widget/maps/map-model.definition.ts
@@ -219,7 +219,8 @@ const getMapDataLayerDatasources = (settings: MapDataLayerSettings[],
   return datasources;
 };
 
-const getMapDataLayersDatasources = (settings: BaseMapSettings, layerTypes: MapDataLayerType[], includeDataKeys = false): Datasource[] => {
+const getMapDataLayersDatasources = (settings: BaseMapSettings,
+                                     layerTypes: readonly MapDataLayerType[], includeDataKeys = false): Datasource[] => {
   const datasources: Datasource[] = [];
   for (const layerType of layerTypes) {
     const dataLayerSettings = settings[layerType];
diff --git a/ui-ngx/src/app/shared/models/widget/maps/map.models.ts b/ui-ngx/src/app/shared/models/widget/maps/map.models.ts
index c846bd0522..edfe03cc05 100644
--- a/ui-ngx/src/app/shared/models/widget/maps/map.models.ts
+++ b/ui-ngx/src/app/shared/models/widget/maps/map.models.ts
@@ -200,9 +200,9 @@ export const defaultBaseDataLayerSettings = (mapType: MapType): Partial<MapDataL
   }
 })
 
-export type MapDataLayerType = 'trips' | 'markers' | 'polygons' | 'circles' | 'polylines';
+export const mapDataLayerTypes = ['trips', 'markers', 'polygons', 'circles', 'polylines'] as const;
 
-export const mapDataLayerTypes: MapDataLayerType[] = ['trips', 'markers', 'polygons', 'circles', 'polylines'];
+export type MapDataLayerType = typeof mapDataLayerTypes[number];
 
 export const latestMapDataLayerTypes: MapDataLayerType[] = ['markers', 'polygons', 'circles', 'polylines'];