diff --git a/kivy/properties.pyx b/kivy/properties.pyx
index 2c0342991..503d9848a 100644
--- a/kivy/properties.pyx
+++ b/kivy/properties.pyx
@@ -171,6 +171,8 @@ __all__ = ('Property',
            'OptionProperty', 'ReferenceListProperty', 'AliasProperty',
            'DictProperty')
 
+include "graphics/config.pxi"
+
 from weakref import ref
 
 cdef float g_dpi = -1
@@ -489,10 +491,16 @@ cdef class StringProperty(Property):
     cdef check(self, EventDispatcher obj, value):
         if Property.check(self, obj, value):
             return True
-        if not isinstance(value, basestring):
-            raise ValueError('%s.%s accept only str/unicode' % (
-                obj.__class__.__name__,
-                self.name))
+        IF PY3:
+            if not isinstance(value, str):
+                raise ValueError('%s.%s accept only str' % (
+                    obj.__class__.__name__,
+                    self.name))
+        ELSE:
+            if not isinstance(value, basestring):
+                raise ValueError('%s.%s accept only str/unicode' % (
+                    obj.__class__.__name__,
+                    self.name))
 
 cdef inline void observable_list_dispatch(object self):
     cdef Property prop = self.prop
diff --git a/setup.py b/setup.py
index ac8abcc98..bb7202781 100644
--- a/setup.py
+++ b/setup.py
@@ -10,6 +10,12 @@ from os import walk, environ
 from distutils.core import setup
 from distutils.extension import Extension
 
+if sys.version > '3':
+    PY3 = True
+else:
+    PY3 = False
+
+
 # -----------------------------------------------------------------------------
 # Detect options
 #
@@ -75,14 +81,15 @@ class KivyBuildExt(build_ext):
         with open(config_h, 'w') as fd:
             fd.write('// Autogenerated file for Kivy C configuration\n')
             for k, v in c_options.items():
-                fd.write('#define __%s %d\n' % (k.upper(), int(v)))
+                fd.write('#define __{0} {1}\n'.format(k.upper(), int(v)))
 
         print('Generate config.pxi')
         config_pxi = join(dirname(__file__), 'kivy', 'graphics', 'config.pxi')
         with open(config_pxi, 'w') as fd:
             fd.write('# Autogenerated file for Kivy Cython configuration\n')
             for k, v in c_options.items():
-                fd.write('DEF %s = %d\n' % (k.upper(), int(v)))
+                fd.write('DEF {0} = {1}\n'.format(k.upper(), int(v)))
+            fd.write('DEF PY3 = {0}\n'.format(int(PY3)))
 
         build_ext.build_extensions(self)