diff --git a/colander/compat.py b/colander/compat.py
index 4e7e598..3a13b54 100644
--- a/colander/compat.py
+++ b/colander/compat.py
@@ -1,7 +1,7 @@
 import sys
 
 PY2 = sys.version_info[0] == 2
-PY3 = sys.version_info[0] == 3
+PY3 = not PY2
 
 if PY2:
     string_types = basestring,