diff --git a/gluon/validators.py b/gluon/validators.py
index e5b9887a..c8398848 100644
--- a/gluon/validators.py
+++ b/gluon/validators.py
@@ -3366,7 +3366,8 @@ class IS_IPV4(Validator):
                     (number == self.localhost)):
                     ok = False
             if not (self.is_private is None or self.is_private ==
-                    (sum([number[0] <= number <= number[1] for number in self.private]) > 0)):
+                    (sum([private_number[0] <= number <= private_number[1] 
+                          for private_number in self.private]) > 0)):
                     ok = False
             if not (self.is_automatic is None or self.is_automatic ==
                     (self.automatic[0] <= number <= self.automatic[1])):