diff --git a/lib/public/AppFramework/Http/FileDisplayResponse.php b/lib/public/AppFramework/Http/FileDisplayResponse.php
index c18404b7d9161..3cd3adf4bfa2f 100644
--- a/lib/public/AppFramework/Http/FileDisplayResponse.php
+++ b/lib/public/AppFramework/Http/FileDisplayResponse.php
@@ -48,8 +48,16 @@ public function __construct(File|ISimpleFile $file, int $statusCode = Http::STAT
 	 */
 	public function callback(IOutput $output) {
 		if ($output->getHttpResponseCode() !== Http::STATUS_NOT_MODIFIED) {
+			$file = $this->file->read();
+
+			if ($file === false) {
+				$output->setHttpResponseCode(Http::STATUS_NOT_FOUND);
+				$output->setOutput('');
+				return;
+			}
+
 			$output->setHeader('Content-Length: ' . $this->file->getSize());
-			$output->setOutput($this->file->getContent());
+			$output->setReadfile($file);
 		}
 	}
 }
diff --git a/tests/lib/AppFramework/Http/FileDisplayResponseTest.php b/tests/lib/AppFramework/Http/FileDisplayResponseTest.php
index 029ddaad7125b..3fc29cb8ac5b9 100644
--- a/tests/lib/AppFramework/Http/FileDisplayResponseTest.php
+++ b/tests/lib/AppFramework/Http/FileDisplayResponseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * SPDX-FileCopyrightText: 2016 Nextcloud GmbH and Nextcloud contributors
  * SPDX-License-Identifier: AGPL-3.0-or-later
@@ -9,19 +11,16 @@
 
 use OCP\AppFramework\Http;
 use OCP\AppFramework\Http\FileDisplayResponse;
+use OCP\AppFramework\Http\IOutput;
 use OCP\Files\File;
+use PHPUnit\Framework\MockObject\MockObject;
 
 class FileDisplayResponseTest extends \Test\TestCase {
-	/** @var File|\PHPUnit\Framework\MockObject\MockObject */
-	private $file;
-
-	/** @var FileDisplayResponse */
-	private $response;
+	private File&MockObject $file;
+	private FileDisplayResponse $response;
 
 	protected function setUp(): void {
-		$this->file = $this->getMockBuilder('OCP\Files\File')
-			->getMock();
-
+		$this->file = $this->createMock(File::class);
 		$this->file->expects($this->once())
 			->method('getETag')
 			->willReturn('myETag');
@@ -52,7 +51,7 @@ public function testLastModified(): void {
 	}
 
 	public function test304(): void {
-		$output = $this->getMockBuilder('OCP\AppFramework\Http\IOutput')
+		$output = $this->getMockBuilder(IOutput::class)
 			->disableOriginalConstructor()
 			->getMock();
 
@@ -69,25 +68,50 @@ public function test304(): void {
 
 
 	public function testNon304(): void {
-		$output = $this->getMockBuilder('OCP\AppFramework\Http\IOutput')
+		$resource = fopen('php://memory', "w+b");
+		fwrite($resource, 'my data');
+		rewind($resource);
+
+		$this->file->expects($this->once())
+			->method('read')
+			->willReturn($resource);
+		$this->file->expects($this->any())
+			->method('getSize')
+			->willReturn(7);
+
+		$output = $this->getMockBuilder(IOutput::class)
 			->disableOriginalConstructor()
 			->getMock();
-
-		$output->expects($this->any())
+		$output->expects($this->once())
 			->method('getHttpResponseCode')
 			->willReturn(Http::STATUS_OK);
 		$output->expects($this->once())
-			->method('setOutput')
-			->with($this->equalTo('my data'));
+			->method('setReadFile')
+			->with($this->equalTo($resource));
 		$output->expects($this->once())
 			->method('setHeader')
-			->with($this->equalTo('Content-Length: 42'));
+			->with($this->equalTo('Content-Length: 7'));
+
+		$this->response->callback($output);
+	}
+
+	public function testFileNotFound(): void {
 		$this->file->expects($this->once())
-			->method('getContent')
-			->willReturn('my data');
-		$this->file->expects($this->any())
-			->method('getSize')
-			->willReturn(42);
+			->method('read')
+			->willReturn(false);
+
+		$output = $this->getMockBuilder(IOutput::class)
+			->disableOriginalConstructor()
+			->getMock();
+		$output->expects($this->once())
+			->method('getHttpResponseCode')
+			->willReturn(Http::STATUS_OK);
+		$output->expects($this->once())
+			->method('setHttpResponseCode')
+			->with($this->equalTo(Http::STATUS_NOT_FOUND));
+		$output->expects($this->once())
+			->method('setOutput')
+			->with($this->equalTo(''));
 
 		$this->response->callback($output);
 	}