diff --git a/apps/files/src/services/DropService.ts b/apps/files/src/services/DropService.ts
index 6d1fbc524c046..91f6e78e974b9 100644
--- a/apps/files/src/services/DropService.ts
+++ b/apps/files/src/services/DropService.ts
@@ -62,7 +62,9 @@ export async function dataTransferToFileTree(items: DataTransferItem[]): Promise
 
 			// Warn the user that the browser does not support the Filesystem API
 			// we therefore cannot upload directories recursively.
-			if (file.type === 'httpd/unix-directory' || !file.type) {
+			// Note: files with an unknown type are kept on purpose, the server
+			// detects their mime type on upload (content sniffing + extension map).
+			if (file.type === 'httpd/unix-directory' || (!file.type && file.size === 0)) {
 				if (!warned) {
 					logger.warn('Browser does not support Filesystem API. Directories will not be uploaded')
 					showWarning(t('files', 'Your browser does not support the Filesystem API. Directories will not be uploaded'))
diff --git a/apps/files/src/services/DropServiceUtils.spec.ts b/apps/files/src/services/DropServiceUtils.spec.ts
index e8d2e2ad33d69..3fc76656bca0c 100644
--- a/apps/files/src/services/DropServiceUtils.spec.ts
+++ b/apps/files/src/services/DropServiceUtils.spec.ts
@@ -219,4 +219,35 @@ describe('DropService dataTransferToFileTree', () => {
 		expect(logger.warn).toHaveBeenNthCalledWith(4, 'Could not get FilesystemEntry of item, falling back to file')
 		expect(logger.warn).toHaveBeenCalledTimes(4)
 	})
+
+	it('Should keep files with an unknown mime type for server-side detection', async () => {
+		const { showWarning } = await import('@nextcloud/dialogs')
+		const file = new File(['data'], 'notes.unknown-ext', { type: '' })
+		const item = Object.create(DataTransferItemMock.prototype)
+		Object.defineProperties(item, {
+			kind: { value: 'file' },
+			getAsFile: { value: () => file },
+		})
+
+		const fileTree = await dataTransferToFileTree([item as unknown as DataTransferItem])
+
+		expect(fileTree.contents).toHaveLength(1)
+		expect(fileTree.contents[0].name).toBe('notes.unknown-ext')
+		expect(showWarning).not.toHaveBeenCalled()
+	})
+
+	it('Should still skip unix directories with a warning', async () => {
+		const { showWarning } = await import('@nextcloud/dialogs')
+		const file = new File([], 'mydir', { type: 'httpd/unix-directory' })
+		const item = Object.create(DataTransferItemMock.prototype)
+		Object.defineProperties(item, {
+			kind: { value: 'file' },
+			getAsFile: { value: () => file },
+		})
+
+		const fileTree = await dataTransferToFileTree([item as unknown as DataTransferItem])
+
+		expect(fileTree.contents).toHaveLength(0)
+		expect(showWarning).toHaveBeenCalledTimes(1)
+	})
 })