diff --git a/os_testr/os_testr.py b/os_testr/os_testr.py
index 83d4140..9751c02 100755
--- a/os_testr/os_testr.py
+++ b/os_testr/os_testr.py
@@ -134,15 +134,18 @@ def construct_regex(blacklist_file, regex, print_exclude):
             raw_line = line.strip()
             split_line = raw_line.split('#')
             # Before the # is the regex
-            regex = split_line[0].strip()
-            # After the # is a comment
-            comment = split_line[1].strip()
-            if regex:
+            line_regex = split_line[0].strip()
+            if len(split_line) > 1:
+                # After the # is a comment
+                comment = split_line[1].strip()
+            else:
+                comment = ''
+            if line_regex:
                 if print_exclude:
-                    print_skips(regex, comment)
-                exclude_regex = '|'.join([regex, exclude_regex])
+                    print_skips(line_regex, comment)
+                exclude_regex = '|'.join([line_regex, exclude_regex])
         if exclude_regex:
-            exclude_regex = "'(?!.*" + exclude_regex + ")"
+            exclude_regex = "(?!.*" + exclude_regex + ")"
     if regex:
         exclude_regex += regex
     return exclude_regex
diff --git a/os_testr/tests/test_os_testr.py b/os_testr/tests/test_os_testr.py
index 9ae6dc5..f820ed1 100644
--- a/os_testr/tests/test_os_testr.py
+++ b/os_testr/tests/test_os_testr.py
@@ -18,7 +18,9 @@ test_os_testr
 
 Tests for `os_testr` module.
 """
+
 import mock
+import six
 
 from os_testr import os_testr
 from os_testr.tests import base
@@ -123,3 +125,101 @@ class TestCallers(base.TestCase):
                                   'call_subunit_run',
                                   side_effect=_fake_run):
             os_testr.main()
+
+
+class TestConstructRegex(base.TestCase):
+    def test_regex_passthrough(self):
+        result = os_testr.construct_regex(None, 'fake_regex', False)
+        self.assertEqual(result, 'fake_regex')
+
+    def test_blacklist_regex_with_comments(self):
+        blacklist_file = six.StringIO()
+        for i in range(4):
+            blacklist_file.write('fake_regex_%s # A Comment\n' % i)
+        blacklist_file.seek(0)
+        with mock.patch('six.moves.builtins.open',
+                        return_value=blacklist_file):
+            result = os_testr.construct_regex('fake_path', None, False)
+        self.assertEqual(
+            result,
+            "(?!.*fake_regex_3|fake_regex_2|fake_regex_1|fake_regex_0|)")
+
+    def test_blacklist_regex_without_comments(self):
+        blacklist_file = six.StringIO()
+        for i in range(4):
+            blacklist_file.write('fake_regex_%s\n' % i)
+        blacklist_file.seek(0)
+        with mock.patch('six.moves.builtins.open',
+                        return_value=blacklist_file):
+            result = os_testr.construct_regex('fake_path', None, False)
+        self.assertEqual(
+            result,
+            "(?!.*fake_regex_3|fake_regex_2|fake_regex_1|fake_regex_0|)")
+
+    def test_blacklist_regex_with_comments_and_regex(self):
+        blacklist_file = six.StringIO()
+        for i in range(4):
+            blacklist_file.write('fake_regex_%s # Comments\n' % i)
+        blacklist_file.seek(0)
+        with mock.patch('six.moves.builtins.open',
+                        return_value=blacklist_file):
+            result = os_testr.construct_regex('fake_path', 'fake_regex', False)
+
+            expected_regex = ("(?!.*fake_regex_3|fake_regex_2|fake_regex_1|"
+                              "fake_regex_0|)fake_regex")
+            self.assertEqual(result, expected_regex)
+
+    def test_blacklist_regex_without_comments_and_regex(self):
+        blacklist_file = six.StringIO()
+        for i in range(4):
+            blacklist_file.write('fake_regex_%s\n' % i)
+        blacklist_file.seek(0)
+        with mock.patch('six.moves.builtins.open',
+                        return_value=blacklist_file):
+            result = os_testr.construct_regex('fake_path', 'fake_regex', False)
+
+            expected_regex = ("(?!.*fake_regex_3|fake_regex_2|fake_regex_1|"
+                              "fake_regex_0|)fake_regex")
+            self.assertEqual(result, expected_regex)
+
+    @mock.patch.object(os_testr, 'print_skips')
+    def test_blacklist_regex_with_comment_print_skips(self, print_mock):
+        blacklist_file = six.StringIO()
+        for i in range(4):
+            blacklist_file.write('fake_regex_%s # Comment\n' % i)
+        blacklist_file.seek(0)
+        with mock.patch('six.moves.builtins.open',
+                        return_value=blacklist_file):
+            result = os_testr.construct_regex('fake_path', None, True)
+
+        expected_regex = ("(?!.*fake_regex_3|fake_regex_2|fake_regex_1|"
+                          "fake_regex_0|)")
+        self.assertEqual(result, expected_regex)
+        calls = print_mock.mock_calls
+        self.assertEqual(len(calls), 4)
+        args = list(map(lambda x: x[1], calls))
+        self.assertIn(('fake_regex_0', 'Comment'), args)
+        self.assertIn(('fake_regex_1', 'Comment'), args)
+        self.assertIn(('fake_regex_2', 'Comment'), args)
+        self.assertIn(('fake_regex_3', 'Comment'), args)
+
+    @mock.patch.object(os_testr, 'print_skips')
+    def test_blacklist_regex_without_comment_print_skips(self, print_mock):
+        blacklist_file = six.StringIO()
+        for i in range(4):
+            blacklist_file.write('fake_regex_%s\n' % i)
+        blacklist_file.seek(0)
+        with mock.patch('six.moves.builtins.open',
+                        return_value=blacklist_file):
+            result = os_testr.construct_regex('fake_path', None, True)
+
+        expected_regex = ("(?!.*fake_regex_3|fake_regex_2|fake_regex_1|"
+                          "fake_regex_0|)")
+        self.assertEqual(result, expected_regex)
+        calls = print_mock.mock_calls
+        self.assertEqual(len(calls), 4)
+        args = list(map(lambda x: x[1], calls))
+        self.assertIn(('fake_regex_0', ''), args)
+        self.assertIn(('fake_regex_1', ''), args)
+        self.assertIn(('fake_regex_2', ''), args)
+        self.assertIn(('fake_regex_3', ''), args)