diff --git a/lib/private/Preview/Generator.php b/lib/private/Preview/Generator.php
index db3b4e87f7..14f113a06d 100644
--- a/lib/private/Preview/Generator.php
+++ b/lib/private/Preview/Generator.php
@@ -87,6 +87,12 @@ class Generator {
 	 * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
 	 */
 	public function getPreview(File $file, $width = -1, $height = -1, $crop = false, $mode = IPreview::MODE_FILL, $mimeType = null) {
+		//Make sure that we can read the file
+		if (!$file->isReadable()) {
+			throw new NotFoundException('Cannot read file');
+		}
+
+
 		$this->eventDispatcher->dispatch(
 			IPreview::EVENT,
 			new GenericEvent($file,[
diff --git a/tests/lib/Preview/GeneratorTest.php b/tests/lib/Preview/GeneratorTest.php
index 130cccdf09..b6200b1829 100644
--- a/tests/lib/Preview/GeneratorTest.php
+++ b/tests/lib/Preview/GeneratorTest.php
@@ -76,6 +76,8 @@ class GeneratorTest extends \Test\TestCase {
 
 	public function testGetCachedPreview() {
 		$file = $this->createMock(File::class);
+		$file->method('isReadable')
+			->willReturn(true);
 		$file->method('getMimeType')
 			->willReturn('myMimeType');
 		$file->method('getId')
@@ -122,6 +124,8 @@ class GeneratorTest extends \Test\TestCase {
 
 	public function testGetNewPreview() {
 		$file = $this->createMock(File::class);
+		$file->method('isReadable')
+			->willReturn(true);
 		$file->method('getMimeType')
 			->willReturn('myMimeType');
 		$file->method('getId')
@@ -248,6 +252,8 @@ class GeneratorTest extends \Test\TestCase {
 		$this->expectException(NotFoundException::class);
 
 		$file = $this->createMock(File::class);
+		$file->method('isReadable')
+			->willReturn(true);
 
 		$this->previewManager->method('isMimeSupported')
 			->with('invalidType')
@@ -271,6 +277,8 @@ class GeneratorTest extends \Test\TestCase {
 
 	public function testNoProvider() {
 		$file = $this->createMock(File::class);
+		$file->method('isReadable')
+			->willReturn(true);
 		$file->method('getMimeType')
 			->willReturn('myMimeType');
 		$file->method('getId')
@@ -350,6 +358,8 @@ class GeneratorTest extends \Test\TestCase {
 	 */
 	public function testCorrectSize($maxX, $maxY, $reqX, $reqY, $crop, $mode, $expectedX, $expectedY) {
 		$file = $this->createMock(File::class);
+		$file->method('isReadable')
+			->willReturn(true);
 		$file->method('getMimeType')
 			->willReturn('myMimeType');
 		$file->method('getId')
@@ -416,4 +426,14 @@ class GeneratorTest extends \Test\TestCase {
 			$this->assertSame($preview, $result);
 		}
 	}
+
+	public function testUnreadbleFile() {
+		$file = $this->createMock(File::class);
+		$file->method('isReadable')
+			->willReturn(false);
+
+		$this->expectException(NotFoundException::class);
+
+		$this->generator->getPreview($file, 100, 100, false);
+	}
 }