diff --git a/Lib/compileall.py b/Lib/compileall.py
index a5c82a3..f99b834 100644
--- a/Lib/compileall.py
+++ b/Lib/compileall.py
@@ -11,10 +11,11 @@
 See module py_compile for details of the actual byte-compilation.
 
 """
-
 import os
 import sys
 import py_compile
+import struct
+import imp
 
 __all__ = ["compile_dir","compile_path"]
 
@@ -54,11 +55,17 @@
         if os.path.isfile(fullname):
             head, tail = name[:-3], name[-3:]
             if tail == '.py':
-                cfile = fullname + (__debug__ and 'c' or 'o')
-                ftime = os.stat(fullname).st_mtime
-                try: ctime = os.stat(cfile).st_mtime
-                except os.error: ctime = 0
-                if (ctime > ftime) and not force: continue
+                if not force:
+                    try:
+                        mtime = os.stat(fullname).st_mtime
+                        expect = struct.pack('<4sl', imp.get_magic(), mtime)
+                        cfile = fullname + (__debug__ and 'c' or 'o')
+                        with open(cfile, 'rb') as chandle:
+                            actual = chandle.read(8)
+                        if expect == actual:
+                            continue
+                    except IOError:
+                        pass
                 if not quiet:
                     print 'Compiling', fullname, '...'
                 try:
@@ -80,7 +87,8 @@
              name != os.curdir and name != os.pardir and \
              os.path.isdir(fullname) and \
              not os.path.islink(fullname):
-            if not compile_dir(fullname, maxlevels - 1, dfile, force, rx, quiet):
+            if not compile_dir(fullname, maxlevels - 1, dfile, force, rx,
+                               quiet):
                 success = 0
     return success