diff --git a/examples/stacked_area_examples.py b/examples/stacked_area_examples.py
index 49c8872..1274205 100644
--- a/examples/stacked_area_examples.py
+++ b/examples/stacked_area_examples.py
@@ -8,6 +8,7 @@
 #Build a Stacked Area Chart from scratch
 
 from vincent import *
+import pandas as pd
 import pandas.io.data as web
 all_data = {}
 for ticker in ['AAPL', 'GOOG', 'IBM', 'YHOO', 'MSFT']:
diff --git a/vincent/visualization.py b/vincent/visualization.py
index 9d8463e..514a7de 100644
--- a/vincent/visualization.py
+++ b/vincent/visualization.py
@@ -86,7 +86,7 @@ def viewport(value):
             if v < 0:
                 raise ValueError('viewport dimensions cannot be negative')
 
-    @grammar((int, dict))
+    @grammar((int, dict, str))
     def padding(value):
         """int or dict : Padding around visualization