diff -r 04ff1cc40d62 Doc/library/inspect.rst
--- a/Doc/library/inspect.rst	Fri Oct 04 11:38:59 2013 -0400
+++ b/Doc/library/inspect.rst	Sun Oct 06 23:15:03 2013 +0800
@@ -341,7 +341,16 @@
 
    Return in a single string any lines of comments immediately preceding the
    object's source code (for a class, function, or method), or at the top of the
-   Python source file (if the object is a module).
+   Python source file (if the object is a module). An :exc:`OSError` is raised
+   if the source code cannot be retrieved, and a :exc:`TypeError` is raised if
+   the object is a built-in module, class or function.
+
+   .. versionchanged:: 3.4
+      :exc:`OSError` is raised if the source code cannot be retrieved, rather
+      than returning ``None``.
+
+      :exc:`TypeError` is raised if the object is a built-in module, class or
+      function, rather than returning ``None``.
 
 
 .. function:: getfile(object)
diff -r 04ff1cc40d62 Lib/inspect.py
--- a/Lib/inspect.py	Fri Oct 04 11:38:59 2013 -0400
+++ b/Lib/inspect.py	Sun Oct 06 23:15:03 2013 +0800
@@ -691,12 +691,10 @@
 def getcomments(object):
     """Get lines of comments immediately preceding an object's source code.
 
-    Returns None when source can't be found.
+    An OSError is raised if the source code cannot be retrieved. A TypeError
+    is raised if object is a built-in module, class or function.
     """
-    try:
-        lines, lnum = findsource(object)
-    except (OSError, TypeError):
-        return None
+    lines, lnum = findsource(object)
 
     if ismodule(object):
         # Look for a comment block at the top of the file.
diff -r 04ff1cc40d62 Lib/test/test_inspect.py
--- a/Lib/test/test_inspect.py	Fri Oct 04 11:38:59 2013 -0400
+++ b/Lib/test/test_inspect.py	Sun Oct 06 23:15:03 2013 +0800
@@ -10,14 +10,18 @@
 import shutil
 import functools
 import importlib
+import textwrap
+import imp
 from os.path import normcase
 try:
     from concurrent.futures import ThreadPoolExecutor
 except ImportError:
     ThreadPoolExecutor = None
 
-from test.support import run_unittest, TESTFN, DirsOnSysPath
-from test.script_helper import assert_python_ok, assert_python_failure
+from test.support import run_unittest, TESTFN, DirsOnSysPath, unlink
+from test.script_helper import (assert_python_ok,
+                                assert_python_failure,
+                                make_script)
 from test import inspect_fodder as mod
 from test import inspect_fodder2 as mod2
 
@@ -223,6 +227,14 @@
 
 class TestRetrievingSourceCode(GetSourceBase):
     fodderModule = mod
+    source_content = textwrap.dedent("""\
+        # line 1
+        'A module docstring.'
+
+        # line 20
+        class StupidGit:
+            pass
+        """)
 
     def test_getclasses(self):
         classes = inspect.getmembers(mod, inspect.isclass)
@@ -282,6 +294,18 @@
     def test_getcomments(self):
         self.assertEqual(inspect.getcomments(mod), '# line 1\n')
         self.assertEqual(inspect.getcomments(mod.StupidGit), '# line 20\n')
+        self.assertRaisesRegex(TypeError, 'built-in',
+                               inspect.getcomments, list)
+        source_file = TESTFN + '.py'
+        self.addCleanup(unlink, source_file)
+        make_script('', TESTFN, self.source_content)
+        spam = imp.load_source('spam', source_file)
+        self.assertEqual(inspect.getcomments(spam), '# line 1\n')
+        self.assertEqual(inspect.getcomments(spam.StupidGit), '# line 20\n')
+        # If the source file is unavailable, it should raise OSError.
+        unlink(source_file)
+        del linecache.cache[source_file]
+        self.assertRaises(OSError, inspect.getcomments, spam)
 
     def test_getmodule(self):
         # Check actual module
@@ -300,6 +324,15 @@
     def test_getsource(self):
         self.assertSourceEqual(git.abuse, 29, 39)
         self.assertSourceEqual(mod.StupidGit, 21, 46)
+        source_file = TESTFN + '.py'
+        self.addCleanup(unlink, source_file)
+        make_script('', TESTFN, self.source_content)
+        spam = imp.load_source('spam', source_file)
+        self.assertEqual(inspect.getsource(spam), self.source_content)
+        # If the source file is unavailable, it should raise OSError.
+        unlink(source_file)
+        del linecache.cache[source_file]
+        self.assertRaises(OSError, inspect.getsource, spam)
 
     def test_getsourcefile(self):
         self.assertEqual(normcase(inspect.getsourcefile(mod.spam)), modfile)