diff -r b66e82c9f852 Lib/importlib/abc.py
--- a/Lib/importlib/abc.py	Tue Jun 26 23:05:27 2012 +0200
+++ b/Lib/importlib/abc.py	Wed Jun 27 07:14:28 2012 -0700
@@ -302,7 +302,16 @@
                     raise
             else:
                 # Bytecode seems fine, so try to use it.
-                return marshal.loads(bytecode)
+                try:
+                    return marshal.loads(bytecode)
+                except ValueError as e:
+                    # Python 3.3 added a file size field, so we might need to
+                    # ignore 4 bytes for that.
+                    bytecode = bytecode[4:]
+                    try:
+                        return marshal.loads(bytecode)
+                    except EOFError:  # If we get EOF, raise original ValueError exception
+                        raise e
         elif source_timestamp is None:
             raise ImportError("no source or bytecode available to create code "
                               "object for {0!r}".format(fullname),