diff --git a/multipart/multipart.py b/multipart/multipart.py
index 27aaecb..5f70a8a 100644
--- a/multipart/multipart.py
+++ b/multipart/multipart.py
@@ -1193,6 +1193,13 @@ def data_callback(name, remaining=False):
                 # Set a mark of our header field.
                 set_mark('header_field')
 
+                # Notify that we're starting a header if the next character is
+                # not a CR; a CR at the beginning of the header will cause us
+                # to stop parsing headers in the STATE_HEADER_FIELD state,
+                # below.
+                if c != CR:
+                    self.callback('header_begin')
+
                 # Move to parsing header fields.
                 state = STATE_HEADER_FIELD
                 i -= 1
diff --git a/multipart/tests/test_multipart.py b/multipart/tests/test_multipart.py
index 7913cd2..1ef5c57 100644
--- a/multipart/tests/test_multipart.py
+++ b/multipart/tests/test_multipart.py
@@ -1244,6 +1244,38 @@ def test_invalid_max_size_multipart(self):
         with self.assertRaises(ValueError):
             q = MultipartParser(b'bound', max_size='foo')
 
+    def test_header_begin_callback(self):
+        """
+        This test verifies we call the `on_header_begin` callback.
+
+        See GitHub issue #23
+        """
+        # Load test data.
+        test_file = 'single_field_single_file.http'
+        with open(os.path.join(http_tests_dir, test_file), 'rb') as f:
+            test_data = f.read()
+
+        calls = []
+        def on_header_begin(*args, **kwargs):
+            calls.append((args, kwargs))
+
+        callbacks = {
+            'on_header_begin': on_header_begin,
+        }
+        parser = MultipartParser('boundary', callbacks,
+                                 max_size=1000)
+
+        # Create multipart parser and feed it
+        i = parser.write(test_data)
+        parser.finalize()
+
+        # Assert we processed everything.
+        self.assertEqual(i, len(test_data))
+
+        # Assert that we called our 'header_begin' callbakc three times; once
+        # for each header in the multipart message.
+        self.assertEqual(len(calls), 3)
+
 
 class TestHelperFunctions(unittest.TestCase):
     def test_create_form_parser(self):