diff --git a/admin/app/services/map_service.ts b/admin/app/services/map_service.ts
index c1157b0..0e1c902 100644
--- a/admin/app/services/map_service.ts
+++ b/admin/app/services/map_service.ts
@@ -301,7 +301,7 @@ export class MapService implements IMapService {
       }
 
       const contentLength = response.headers['content-length']
-      const size = contentLength ? parseInt(contentLength, 10) : 0
+      const size = contentLength ? parseInt(contentLength.toString(), 10) : 0
 
       return { filename, size }
     } catch (error: any) {
diff --git a/admin/app/utils/downloads.ts b/admin/app/utils/downloads.ts
index 23988da..bfe189a 100644
--- a/admin/app/utils/downloads.ts
+++ b/admin/app/utils/downloads.ts
@@ -54,8 +54,8 @@ export async function doResumableDownload({
   // Without this default, the validator below throws `MIME type  is not allowed`
   // and breaks all downloads from kiwix's primary host (#848).
   const contentType =
-    headResponse.headers['content-type'] || 'application/octet-stream'
-  const totalBytes = parseInt(headResponse.headers['content-length'] || '0')
+    headResponse.headers['content-type']?.toString() || 'application/octet-stream'
+  const totalBytes = parseInt(headResponse.headers['content-length']?.toString() || '0', 10)
   const supportsRangeRequests = headResponse.headers['accept-ranges'] === 'bytes'
 
   // If allowedMimeTypes is provided, check content type