diff --git a/lib/private/Preview/Generator.php b/lib/private/Preview/Generator.php
index f7aed987d8..45e991d551 100644
--- a/lib/private/Preview/Generator.php
+++ b/lib/private/Preview/Generator.php
@@ -192,6 +192,12 @@ class Generator {
 			}
 		}
 
+		// Free memory being used by the embedded image resource.  Without this the image is kept in memory indefinitely.
+		// Garbage Collection does NOT free this memory.  We have to do it ourselves.
+		if ($maxPreviewImage instanceof IImage) {
+			$maxPreviewImage->destroy();
+		}
+
 		return $preview;
 	}
 
diff --git a/tests/lib/Preview/GeneratorTest.php b/tests/lib/Preview/GeneratorTest.php
index 3a46447632..5e9b9bcbb8 100644
--- a/tests/lib/Preview/GeneratorTest.php
+++ b/tests/lib/Preview/GeneratorTest.php
@@ -31,7 +31,6 @@ use OCP\Files\NotFoundException;
 use OCP\Files\SimpleFS\ISimpleFile;
 use OCP\Files\SimpleFS\ISimpleFolder;
 use OCP\IConfig;
-use OCP\IImage;
 use OCP\IPreview;
 use OCP\Preview\IProviderV2;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
@@ -183,7 +182,7 @@ class GeneratorTest extends \Test\TestCase {
 				$this->fail('Unexpected provider requested');
 			});
 
-		$image = $this->createMock(IImage::class);
+		$image = $this->createMock(\OC_Image::class);
 		$image->method('width')->willReturn(2048);
 		$image->method('height')->willReturn(2048);
 		$image->method('valid')->willReturn(true);
@@ -318,7 +317,7 @@ class GeneratorTest extends \Test\TestCase {
 	}
 
 	private function getMockImage($width, $height, $data = null) {
-		$image = $this->createMock(IImage::class);
+		$image = $this->createMock(\OC_Image::class);
 		$image->method('height')->willReturn($width);
 		$image->method('width')->willReturn($height);
 		$image->method('valid')->willReturn(true);