diff --git a/jinja2/tests.py b/jinja2/tests.py
index 50510b0..74017e5 100644
--- a/jinja2/tests.py
+++ b/jinja2/tests.py
@@ -10,6 +10,7 @@
 """
 import re
 from jinja2.runtime import Undefined
+import six
 
 try:
     from collections import Mapping as MappingType
@@ -76,12 +77,12 @@
 
 def test_lower(value):
     """Return true if the variable is lowercased."""
-    return unicode(value).islower()
+    return six.text_type(value).islower()
 
 
 def test_upper(value):
     """Return true if the variable is uppercased."""
-    return unicode(value).isupper()
+    return six.text_type(value).isupper()
 
 
 def test_string(value):