diff --git a/cpplint/cpplint.py b/cpplint/cpplint.py
index b12d60d..e98e572 100755
--- a/cpplint/cpplint.py
+++ b/cpplint/cpplint.py
@@ -550,7 +550,7 @@ _valid_extensions = set(['cc', 'h', 'cpp', 'cu', 'cuh'])
 
 # Treat all headers starting with 'h' equally: .h, .hpp, .hxx etc.
 # This is set by --headers flag.
-_hpp_headers = None
+_hpp_headers = set(['h'])
 
 # {str, bool}: a map from error categories to booleans which indicate if the
 # category should be suppressed for every line.
@@ -566,10 +566,7 @@ def ProcessHppHeadersOption(val):
     PrintUsage('Header extensions must be comma seperated list.')
 
 def IsHeaderExtension(file_extension):
-  if _hpp_headers and file_extension in _hpp_headers:
-    return True
-  else:
-    return file_extension == 'h'
+  return file_extension in _hpp_headers
 
 def ParseNolintSuppressions(filename, raw_line, linenum, error):
   """Updates the global list of line error-suppressions.
diff --git a/cpplint/cpplint_unittest.py b/cpplint/cpplint_unittest.py
index d738d99..638bbc2 100755
--- a/cpplint/cpplint_unittest.py
+++ b/cpplint/cpplint_unittest.py
@@ -3778,6 +3778,7 @@ class CpplintTest(CpplintTestBase):
     old_error_categories = cpplint._ERROR_CATEGORIES
     old_output_format = cpplint._cpplint_state.output_format
     old_verbose_level = cpplint._cpplint_state.verbose_level
+    old_headers = cpplint._hpp_headers
     old_filters = cpplint._cpplint_state.filters
     old_line_length = cpplint._line_length
     old_valid_extensions = cpplint._valid_extensions
@@ -3795,6 +3796,7 @@ class CpplintTest(CpplintTestBase):
       self.assertRaises(SystemExit, cpplint.ParseArguments, ['--filter=foo'])
       self.assertRaises(SystemExit, cpplint.ParseArguments,
                         ['--filter=+a,b,-c'])
+      self.assertRaises(SystemExit, cpplint.ParseArguments, ['--headers'])
 
       self.assertEquals(['foo.cc'], cpplint.ParseArguments(['foo.cc']))
       self.assertEquals(old_output_format, cpplint._cpplint_state.output_format)
@@ -3837,6 +3839,13 @@ class CpplintTest(CpplintTestBase):
       self.assertEqual(['foo.h'],
                        cpplint.ParseArguments(['--extensions=hpp,cpp,cpp', 'foo.h']))
       self.assertEqual(set(['hpp', 'cpp']), cpplint._valid_extensions)
+      
+      self.assertEqual(set(['h']), cpplint._hpp_headers)  # Default value
+      self.assertEqual(['foo.h'],
+                       cpplint.ParseArguments(['--extensions=cpp,cpp', '--headers=hpp,h', 'foo.h']))
+      self.assertEqual(set(['hpp', 'h']), cpplint._hpp_headers)
+      self.assertEqual(set(['hpp', 'h', 'cpp']), cpplint._valid_extensions)
+      
     finally:
       cpplint._USAGE = old_usage
       cpplint._ERROR_CATEGORIES = old_error_categories
@@ -3845,6 +3854,7 @@ class CpplintTest(CpplintTestBase):
       cpplint._cpplint_state.filters = old_filters
       cpplint._line_length = old_line_length
       cpplint._valid_extensions = old_valid_extensions
+      cpplint._hpp_headers = old_headers
 
   def testLineLength(self):
     old_line_length = cpplint._line_length