diff -r 89af3880ca57 Lib/distutils/tests/test_build_py.py
--- a/Lib/distutils/tests/test_build_py.py	Mon Mar 14 11:57:16 2011 -0400
+++ b/Lib/distutils/tests/test_build_py.py	Mon Mar 14 17:43:02 2011 -0400
@@ -1,5 +1,6 @@
 """Tests for distutils.command.build_py."""
 
+import imp
 import os
 import sys
 import io
@@ -57,8 +58,10 @@
         self.assertEqual(len(cmd.get_outputs()), 3)
         pkgdest = os.path.join(destination, "pkg")
         files = os.listdir(pkgdest)
+        byte_compiled_files = os.listdir(os.path.join(pkgdest, "__pycache__"))
         self.assertTrue("__init__.py" in files)
-        self.assertTrue("__init__.pyc" in files)
+        self.assertTrue("__init__.{0}.pyc".format(imp.get_tag())
+            in byte_compiled_files)
         self.assertTrue("README.txt" in files)
 
     def test_empty_package_dir (self):
diff -r 89af3880ca57 Lib/distutils/tests/test_install_lib.py
--- a/Lib/distutils/tests/test_install_lib.py	Mon Mar 14 11:57:16 2011 -0400
+++ b/Lib/distutils/tests/test_install_lib.py	Mon Mar 14 17:43:02 2011 -0400
@@ -1,4 +1,5 @@
 """Tests for distutils.command.install_data."""
+import imp
 import sys
 import os
 import unittest
@@ -36,14 +37,19 @@
                          'byte-compile not supported')
     def test_byte_compile(self):
         pkg_dir, dist = self.create_dist()
+        cache_dir = os.path.join(pkg_dir, '__pycache__')
         cmd = install_lib(dist)
         cmd.compile = cmd.optimize = 1
 
         f = os.path.join(pkg_dir, 'foo.py')
         self.write_file(f, '# python file')
         cmd.byte_compile([f])
-        self.assertTrue(os.path.exists(os.path.join(pkg_dir, 'foo.pyc')))
-        self.assertTrue(os.path.exists(os.path.join(pkg_dir, 'foo.pyo')))
+        compiled_file = os.path.join(cache_dir,
+                "foo.{magic_tag}.pyc".format(magic_tag=imp.get_tag()))
+        optimized_file = os.path.join(cache_dir,
+                "foo.{magic_tag}.pyo".format(magic_tag=imp.get_tag()))
+        self.assertTrue(os.path.exists(compiled_file))
+        self.assertTrue(os.path.exists(optimized_file))
 
     def test_get_outputs(self):
         pkg_dir, dist = self.create_dist()
diff -r 89af3880ca57 Lib/distutils/util.py
--- a/Lib/distutils/util.py	Mon Mar 14 11:57:16 2011 -0400
+++ b/Lib/distutils/util.py	Mon Mar 14 17:43:02 2011 -0400
@@ -6,7 +6,7 @@
 
 __revision__ = "$Id$"
 
-import sys, os, string, re
+import sys, os, string, re, imp
 from distutils.errors import DistutilsPlatformError
 from distutils.dep_util import newer
 from distutils.spawn import spawn
@@ -533,7 +533,10 @@
             # Terminology from the py_compile module:
             #   cfile - byte-compiled file
             #   dfile - purported source filename (same as 'file' by default)
-            cfile = file + (__debug__ and "c" or "o")
+            if optimize >= 0:
+                cfile = imp.cache_from_source(file, debug_override=not optimize)
+            else:
+                cfile = imp.cache_from_source(file)
             dfile = file
             if prefix:
                 if file[:len(prefix)] != prefix: