diff --git a/package.json b/package.json
index 5a33972fd1..49d03f0821 100644
--- a/package.json
+++ b/package.json
@@ -117,7 +117,7 @@
         "emojibase-regex": "15.3.2",
         "escape-html": "^1.0.3",
         "file-saver": "^2.0.5",
-        "filesize": "10.1.6",
+        "filesize": "11.0.2",
         "github-markdown-css": "^5.5.1",
         "glob-to-regexp": "^0.4.1",
         "highlight.js": "^11.3.1",
diff --git a/src/utils/FileUtils.ts b/src/utils/FileUtils.ts
index 1240dc61db..7958489057 100644
--- a/src/utils/FileUtils.ts
+++ b/src/utils/FileUtils.ts
@@ -7,16 +7,7 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import {
-    filesize,
-    type FileSizeOptionsArray,
-    type FileSizeOptionsBase,
-    type FileSizeOptionsExponent,
-    type FileSizeOptionsObject,
-    type FileSizeOptionsString,
-    type FileSizeReturnArray,
-    type FileSizeReturnObject,
-} from "filesize";
+import { filesize, type FilesizeOptions, type FilesizeReturn } from "filesize";
 import { type MediaEventContent } from "matrix-js-sdk/src/types";
 
 import { _t } from "../languageHandler";
@@ -27,7 +18,7 @@ export function downloadLabelForFile(content: MediaEventContent, withSize = true
     if (content.info?.size && withSize) {
         // If we know the size of the file then add it as human-readable string to the end of the link text
         // so that the user knows how big a file they are downloading.
-        text += " (" + <string>fileSize(content.info.size, { base: 2, standard: "jedec" }) + ")";
+        text += " (" + fileSize(content.info.size, { base: 2, standard: "jedec" }) + ")";
     }
     return text;
 }
@@ -83,18 +74,11 @@ export function presentableTextForFile(
         // it since it is "ugly", users generally aren't aware what it
         // means and the type of the attachment can usually be inferred
         // from the file extension.
-        text += " (" + <string>fileSize(content.info.size, { base: 2, standard: "jedec" }) + ")";
+        text += " (" + fileSize(content.info.size, { base: 2, standard: "jedec" }) + ")";
     }
     return text;
 }
 
-type FileSizeOptions =
-    | FileSizeOptionsString
-    | FileSizeOptionsBase
-    | FileSizeOptionsArray
-    | FileSizeOptionsExponent
-    | FileSizeOptionsObject;
-
 /**
  * wrapper function to set default values for filesize function
  *
@@ -106,15 +90,7 @@ type FileSizeOptions =
  *  exponent: number;
  *  unit: string;}} formatted file size with unit e.g. 12kB, 12KB
  */
-export function fileSize(byteCount: number, options: FileSizeOptionsString | FileSizeOptionsBase): string;
-export function fileSize(byteCount: number, options: FileSizeOptionsArray): FileSizeReturnArray;
-export function fileSize(byteCount: number, options: FileSizeOptionsExponent): number;
-export function fileSize(byteCount: number, options: FileSizeOptionsObject): FileSizeReturnObject;
-export function fileSize(byteCount: number): string;
-export function fileSize(
-    byteCount: number,
-    options?: FileSizeOptions,
-): string | number | FileSizeReturnArray | FileSizeReturnObject {
-    const defaultOption: FileSizeOptions = { base: 2, standard: "jedec", ...options };
-    return filesize(byteCount, defaultOption);
+export function fileSize<O extends FilesizeOptions>(byteCount: number, options?: O): FilesizeReturn<O> {
+    const defaultOption = { base: 2, standard: "jedec", ...options } as O;
+    return filesize<O>(byteCount, defaultOption);
 }
diff --git a/yarn.lock b/yarn.lock
index bdac5418fc..5d47ac3811 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -8108,10 +8108,10 @@ filelist@^1.0.4:
   dependencies:
     minimatch "^5.0.1"
 
-filesize@10.1.6:
-  version "10.1.6"
-  resolved "https://registry.yarnpkg.com/filesize/-/filesize-10.1.6.tgz#31194da825ac58689c0bce3948f33ce83aabd361"
-  integrity sha512-sJslQKU2uM33qH5nqewAwVB2QgR6w1aMNsYUp3aN5rMRyXEwJGmZvaWzeJFNTOXWlHQyBFCWrdj3fV/fsTOX8w==
+filesize@11.0.2:
+  version "11.0.2"
+  resolved "https://registry.yarnpkg.com/filesize/-/filesize-11.0.2.tgz#b7771e3836812582ad74b8a10d6eb0dc58c1ceda"
+  integrity sha512-s/iAeeWLk5BschUIpmdrF8RA8lhFZ/xDZgKw1Tan72oGws1/dFGB06nYEiyyssWUfjKNQTNRlrwMVjO9/hvXDw==
 
 fill-range@^7.1.1:
   version "7.1.1"