diff --git a/imagekit/generatorlibrary.py b/imagekit/generatorlibrary.py
index bc5a0f8..f07e606 100644
--- a/imagekit/generatorlibrary.py
+++ b/imagekit/generatorlibrary.py
@@ -4,9 +4,9 @@ from .specs import ImageSpec
 
 
 class Thumbnail(ImageSpec):
-    def __init__(self, width=None, height=None, anchor=None, crop=None, **kwargs):
+    def __init__(self, width=None, height=None, anchor=None, crop=None, upscale=None, **kwargs):
         self.processors = [ThumbnailProcessor(width, height, anchor=anchor,
-                                              crop=crop)]
+                                              crop=crop, upscale=upscale)]
         super(Thumbnail, self).__init__(**kwargs)