diff --git a/src/lib/components/molecules/Categories/service.ts b/src/lib/components/molecules/Categories/service.ts
index 683d516..2a2a3e0 100644
--- a/src/lib/components/molecules/Categories/service.ts
+++ b/src/lib/components/molecules/Categories/service.ts
@@ -1,5 +1,7 @@
+import type { DataKey } from "$lib/modules/filesystem";
+
 export interface SelectedCategory {
   id: number;
-  dataKey?: { key: CryptoKey; version: Date };
+  dataKey?: DataKey;
   name: string;
 }
diff --git a/src/lib/modules/file/download.svelte.ts b/src/lib/modules/file/download.svelte.ts
index e80fe31..bea8316 100644
--- a/src/lib/modules/file/download.svelte.ts
+++ b/src/lib/modules/file/download.svelte.ts
@@ -18,7 +18,7 @@ export interface FileDownloadState {
   result?: ArrayBuffer;
 }
 
-export type LiveFileDownloadState = FileDownloadState & {
+type LiveFileDownloadState = FileDownloadState & {
   status: "download-pending" | "downloading" | "decryption-pending" | "decrypting";
 };
 
@@ -34,9 +34,7 @@ export const getFileDownloadState = (fileId: number) => {
 };
 
 export const getDownloadingFiles = () => {
-  return downloadingFiles.filter((file): file is LiveFileDownloadState =>
-    isFileDownloading(file.status),
-  );
+  return downloadingFiles.filter((file) => isFileDownloading(file.status));
 };
 
 export const clearDownloadedFiles = () => {
diff --git a/src/lib/modules/filesystem/internal.svelte.ts b/src/lib/modules/filesystem/internal.svelte.ts
index 7bfe60d..f5e5e1f 100644
--- a/src/lib/modules/filesystem/internal.svelte.ts
+++ b/src/lib/modules/filesystem/internal.svelte.ts
@@ -3,7 +3,7 @@ import { unwrapDataKey, decryptString } from "$lib/modules/crypto";
 export class FilesystemCache<K, V extends RV, RV = V> {
   private map = new Map<K, V | Promise<V>>();
 
-  get(key: K, loader: (isInitial: boolean, resolve: (value: RV) => void) => void) {
+  get(key: K, loader: (isInitial: boolean, resolve: (value: RV | undefined) => void) => void) {
     const info = this.map.get(key);
     if (info instanceof Promise) {
       return info;
@@ -15,6 +15,8 @@ export class FilesystemCache<K, V extends RV, RV = V> {
     }
 
     loader(!info, (loadedInfo) => {
+      if (!loadedInfo) return;
+
       let info = this.map.get(key)!;
       if (info instanceof Promise) {
         const state = $state(loadedInfo);
diff --git a/src/lib/modules/filesystem/types.ts b/src/lib/modules/filesystem/types.ts
index fe3254f..6374474 100644
--- a/src/lib/modules/filesystem/types.ts
+++ b/src/lib/modules/filesystem/types.ts
@@ -1,4 +1,4 @@
-type DataKey = { key: CryptoKey; version: Date };
+export type DataKey = { key: CryptoKey; version: Date };
 
 interface LocalDirectoryInfo {
   id: number;
@@ -13,7 +13,6 @@ interface RootDirectoryInfo {
   id: "root";
   parentId?: undefined;
   dataKey?: undefined;
-  dataKeyVersion?: undefined;
   name?: undefined;
   subDirectories: SubDirectoryInfo[];
   files: SummarizedFileInfo[];
@@ -39,7 +38,7 @@ export type CategoryFileInfo = SummarizedFileInfo & { isRecursive: boolean };
 
 interface LocalCategoryInfo {
   id: number;
-  dataKey?: DataKey | undefined;
+  dataKey?: DataKey;
   name: string;
   subCategories: SubCategoryInfo[];
   files: CategoryFileInfo[];
diff --git a/src/lib/utils/promise.ts b/src/lib/utils/promise.ts
index a4b0fb2..9e841c8 100644
--- a/src/lib/utils/promise.ts
+++ b/src/lib/utils/promise.ts
@@ -1,16 +1,16 @@
 export const monotonicResolve = <T>(
-  promises: (Promise<T | undefined> | false)[],
+  promises: (Promise<T> | false)[],
   callback: (value: T) => void,
 ) => {
   let latestResolvedIndex = -1;
-
-  promises.forEach((promise, index) => {
-    if (!promise) return;
-    promise.then((value) => {
-      if (value !== undefined && index > latestResolvedIndex) {
-        latestResolvedIndex = index;
-        callback(value);
-      }
+  promises
+    .filter((promise) => !!promise)
+    .forEach((promise, index) => {
+      promise.then((value) => {
+        if (index > latestResolvedIndex) {
+          latestResolvedIndex = index;
+          callback(value);
+        }
+      });
     });
-  });
 };
diff --git a/src/routes/(main)/directory/[[id]]/service.svelte.ts b/src/routes/(main)/directory/[[id]]/service.svelte.ts
index 0dc69d9..f83bbaf 100644
--- a/src/routes/(main)/directory/[[id]]/service.svelte.ts
+++ b/src/routes/(main)/directory/[[id]]/service.svelte.ts
@@ -8,13 +8,14 @@ import {
   deleteFileThumbnailCache,
   uploadFile,
 } from "$lib/modules/file";
+import type { DataKey } from "$lib/modules/filesystem";
 import { hmacSecretStore, type MasterKey, type HmacSecret } from "$lib/stores";
 import { trpc } from "$trpc/client";
 
 export interface SelectedEntry {
   type: "directory" | "file";
   id: number;
-  dataKey: { key: CryptoKey; version: Date } | undefined;
+  dataKey: DataKey | undefined;
   name: string;
 }