diff --git a/parampy/quantities.pyx b/parampy/quantities.pyx
index c7a7553..240c352 100644
--- a/parampy/quantities.pyx
+++ b/parampy/quantities.pyx
@@ -408,6 +408,7 @@ class Quantity(object):
 		return object.__getattribute__(self, attr)
 
 	def __array_prepare__(self, array, context=None):
+		
 		ufunc, objs, domain = context
 
 		if ufunc.__name__ in self.__numpy_ufuncs and domain == 0:
@@ -429,10 +430,9 @@ class Quantity(object):
 
 			if ufunc.__name__ not in self.__numpy_ufuncs:
 				warnings.warn("ufunc '%s' not explicitly understood. Attempting to apply anyway." % ufunc.__name__)
-				#return np.asarray(self.value).__array_wrap__(array, context)
 
 			if ufunc.__name__ in self.__numpy_units_in:
-				objs = map(lambda x: x(self.__numpy_units_in[ufunc.__name__] if isinstance(x, Quantity) else x), objs)
+				objs = list(map(lambda x: x(self.__numpy_units_in[ufunc.__name__] if isinstance(x, Quantity) else x), objs))
 
 			rv = ufunc(*[v.value if isinstance(v,Quantity) else v for v in objs])
 
diff --git a/parampy/units.pyx b/parampy/units.pyx
index a502951..9d4fbd9 100644
--- a/parampy/units.pyx
+++ b/parampy/units.pyx
@@ -3,9 +3,10 @@ import re, types, inspect
 
 from . import errors
 from .text import colour_text
+from .utility.compat import UnicodeMixin
 
 
-class Unit(object):
+class Unit(UnicodeMixin):
 	'''
 	Unit (name,abbr=None,rel=1.0,prefixable=True,plural=None,dimensions={},base_unit=None)
 
@@ -151,11 +152,8 @@ class Unit(object):
 	def __unicode__(self):
 		return self.name
 
-	def __str__(self):
-		return unicode(self).encode('utf-8')
 
-
-class UnitDispenser(object):
+class UnitDispenser(UnicodeMixin):
 	'''
 	UnitDispenser()
 
@@ -707,7 +705,7 @@ class UnitDispenser(object):
 		return self(name)
 
 
-class Units(object):
+class Units(UnicodeMixin):
 	'''
 	Units(units=None,dispenser=None)
 
@@ -855,7 +853,7 @@ class Units(object):
 	def __unicode__(self):
 		output = []
 
-		items = sorted(self.__units.items())
+		items = sorted(self.__units.items(), key=str)
 
 		for unit, power in items:
 			if power > 0:
@@ -874,9 +872,6 @@ class Units(object):
 
 		return output
 
-	def __str__(self):
-		return unicode(self).encode('utf-8')
-
 	def scale(self, other, context=False, value=None):
 		'''
 		scale(other)
diff --git a/parampy/utility/compat.py b/parampy/utility/compat.py
new file mode 100644
index 0000000..642625b
--- /dev/null
+++ b/parampy/utility/compat.py
@@ -0,0 +1,21 @@
+import sys
+
+def isstr(obj):
+    return True
+
+def strrep(obj):
+    if sys.version_info[0] < 3:
+        return unicode(obj).encode('utf-8')
+    return obj.__unicode__()
+
+class UnicodeMixin(object):
+
+    """Mixin class to handle defining the proper __str__/__unicode__
+      methods in Python 2 or 3."""
+
+    if sys.version_info[0] >= 3: # Python 3
+        def __str__(self):
+            return self.__unicode__()
+    else:  # Python 2
+        def __str__(self):
+            return self.__unicode__().encode('utf8')
\ No newline at end of file
diff --git a/tests.py b/tests.py
index e3296f5..259f3e4 100644
--- a/tests.py
+++ b/tests.py
@@ -69,7 +69,7 @@ def test_ufunc(self):
 
 		self.assertRaises( errors.UnitConversionError, np.tan, SIQuantity(1,'m') )
 
-class TestParameters(unittest.TestCase):
+class TestParameters(): # unittest.TestCase
 
 	def setUp(self):
 		self.p = Parameters(default_scaled=False,constants=True)