diff -r 9623c83ba489 Lib/importlib/abc.py
--- a/Lib/importlib/abc.py	Wed Jun 27 15:26:26 2012 -0400
+++ b/Lib/importlib/abc.py	Wed Jun 27 13:57:41 2012 -0700
@@ -282,7 +282,11 @@
                 if len(raw_timestamp) < 4:
                     raise EOFError("bad timestamp in {}".format(fullname))
                 pyc_timestamp = _bootstrap._r_long(raw_timestamp)
-                bytecode = data[8:]
+                raw_file_size = data[8:12]
+                if len(raw_file_size) < 4:
+                    raise EOFError("bad file size in {}".format(fullname))
+                file_size = _bootstrap._r_long(raw_file_size)
+                bytecode = data[12:]
                 # Verify that the magic number is valid.
                 if imp.get_magic() != magic:
                     raise ImportError(
@@ -318,6 +322,7 @@
         if not sys.dont_write_bytecode:
             data = bytearray(imp.get_magic())
             data.extend(_bootstrap._w_long(source_timestamp))
+            data.extend(_bootstrap._w_long(source_timestamp))
             data.extend(marshal.dumps(code_object))
             self.write_bytecode(fullname, data)
         return code_object
diff -r 9623c83ba489 Lib/importlib/test/source/test_abc_loader.py
--- a/Lib/importlib/test/source/test_abc_loader.py	Wed Jun 27 15:26:26 2012 -0400
+++ b/Lib/importlib/test/source/test_abc_loader.py	Wed Jun 27 13:57:41 2012 -0700
@@ -152,7 +152,8 @@
                 bc = data['bc']
             else:
                 bc = self.compile_bc(name)
-            self.module_bytecode[name] = magic + mtime + bc
+            size = importlib._w_long(len(bc))
+            self.module_bytecode[name] = magic + mtime + size + bc
 
     def compile_bc(self, name):
         source_path = self.module_paths.get(name, '<test>') or '<test>'
@@ -344,7 +345,7 @@
         self.assertEqual(magic, imp.get_magic())
         mtime = importlib._r_long(mock.module_bytecode[name][4:8])
         self.assertEqual(mtime, 1)
-        bc = mock.module_bytecode[name][8:]
+        bc = mock.module_bytecode[name][12:]
         self.assertEqual(bc, mock.compile_bc(name))
 
     def test_module(self):
@@ -456,6 +457,22 @@
         mtime = importlib._r_long(mock.module_bytecode[name][4:8])
         self.assertEqual(mtime, PyPycLoaderMock.default_mtime)
 
+    @source_util.writes_bytecode_files
+    def test_pyc_compatibility(self):
+        name = 'foo'
+        with source_util.create_modules(name) as fpath:
+            loader = importlib.machinery.SourceFileLoader(name, fpath[name])
+            module = loader.load_module(name)
+            bytecode_path = module.__cached__
+            with open(bytecode_path, 'rb') as f:
+                cached_data = f.read()
+            mock = PyPycLoaderMock({name: fpath[name]},
+                                            {name: {'path': bytecode_path}})
+            mock.module_bytecode[name] = cached_data
+            del sys.modules[name]
+            mock.load_module(name)
+            self.assertEqual(mock.module_bytecode[name], cached_data)
+
 
 class BadBytecodeFailureTests(unittest.TestCase):