diff --git a/requests/models.py b/requests/models.py
index 087f8027..ee2ca9e2 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -91,7 +91,7 @@ class RequestEncodingMixin(object):
         """Build the body for a multipart/form-data request.
 
         Will successfully encode files when passed as a dict or a list of
-        2-tuples. Order is retained if data is a list of 2-tuples but abritrary
+        2-tuples. Order is retained if data is a list of 2-tuples but arbitrary
         if parameters are supplied as a dict.
 
         """