diff --git a/Lib/urllib/error.py b/Lib/urllib/error.py
index 237ed6b..45b7169 100644
--- a/Lib/urllib/error.py
+++ b/Lib/urllib/error.py
@@ -1,6 +1,6 @@
 """Exception classes raised by urllib.
 
-The base exception class is URLError, which inherits from IOError.  It
+The base exception class is URLError, which inherits from OSError.  It
 doesn't define any behavior of its own, but is the base class for all
 exceptions defined in this package.
 
@@ -17,11 +17,11 @@
 
 
 # do these error classes make sense?
-# make sure all of the IOError stuff is overridden.  we just want to be
+# make sure all of the OSError stuff is overridden.  we just want to be
 # subtypes.
 
-class URLError(IOError):
-    # URLError is a sub-type of IOError, but it doesn't share any of
+class URLError(OSError):
+    # URLError is a sub-type of OSError, but it doesn't share any of
     # the implementation.  need to override __init__ and __str__.
     # It sets self.args for compatibility with other EnvironmentError
     # subclasses, but args doesn't have the typical format with errno in