diff --git a/docs/guide/gridfs.rst b/docs/guide/gridfs.rst
index d81bb922..596585de 100644
--- a/docs/guide/gridfs.rst
+++ b/docs/guide/gridfs.rst
@@ -20,7 +20,7 @@ a document is created to store details about animals, including a photo::
 
     marmot = Animal(genus='Marmota', family='Sciuridae')
 
-    marmot_photo = open('marmot.jpg', 'r')
+    marmot_photo = open('marmot.jpg', 'rb')
     marmot.photo.put(marmot_photo, content_type = 'image/jpeg')
     marmot.save()
 
@@ -70,5 +70,5 @@ Replacing files
 Files can be replaced with the :func:`replace` method. This works just like
 the :func:`put` method so even metadata can (and should) be replaced::
 
-    another_marmot = open('another_marmot.png', 'r')
+    another_marmot = open('another_marmot.png', 'rb')
     marmot.photo.replace(another_marmot, content_type='image/png')