diff --git a/lib/private/Preview/Imaginary.php b/lib/private/Preview/Imaginary.php
index d421da74ac824..2772d35f71078 100644
--- a/lib/private/Preview/Imaginary.php
+++ b/lib/private/Preview/Imaginary.php
@@ -146,7 +146,9 @@ public function getCroppedThumbnail(File $file, int $maxX, int $maxY, bool $crop
 				$imaginaryUrl . '/pipeline', [
 					'query' => ['operations' => json_encode($operations), 'key' => $imaginaryKey],
 					'stream' => true,
-					'content-type' => $file->getMimeType(),
+					'headers' => [
+						'Content-Type' => $file->getMimeType(),
+					],
 					'body' => $stream,
 					'nextcloud' => ['allow_local_address' => true],
 					'timeout' => 120,