diff --git a/dkim/tests/__init__.py b/dkim/tests/__init__.py
index fad9629..7fb38ab 100644
--- a/dkim/tests/__init__.py
+++ b/dkim/tests/__init__.py
@@ -22,9 +22,11 @@ import unittest
 def test_suite():
     from dkim.tests import (
         test_dkim,
+        test_util,
         )
     modules = [
         test_dkim,
+        test_util,
         ]
     suites = map(lambda x: x.test_suite(), modules)
     return unittest.TestSuite(suites)
diff --git a/dkim/tests/test_dkim.py b/dkim/tests/test_dkim.py
index f4ca775..f499104 100644
--- a/dkim/tests/test_dkim.py
+++ b/dkim/tests/test_dkim.py
@@ -20,11 +20,6 @@ import os.path
 import unittest
 
 import dkim
-from dkim.util import (
-    DuplicateTag,
-    InvalidTagSpec,
-    parse_tag_value,
-    )
 
 
 def read_test_data(filename):
@@ -73,45 +68,6 @@ class TestSignAndVerify(unittest.TestCase):
         self.assertFalse(res)
 
 
-class TestParseTagValue(unittest.TestCase):
-    """Tag=Value parsing tests."""
-
-    def test_single(self):
-        self.assertEqual(
-            {'foo': 'bar'},
-            parse_tag_value('foo=bar'))
-
-    def test_trailing_separator_ignored(self):
-        self.assertEqual(
-            {'foo': 'bar'},
-            parse_tag_value('foo=bar;'))
-
-    def test_multiple(self):
-        self.assertEqual(
-            {'foo': 'bar', 'baz': 'foo'},
-            parse_tag_value('foo=bar;baz=foo'))
-
-    def test_value_with_equals(self):
-        self.assertEqual(
-            {'foo': 'bar', 'baz': 'foo=bar'},
-            parse_tag_value('foo=bar;baz=foo=bar'))
-
-    def test_whitespace_is_stripped(self):
-        self.assertEqual(
-            {'foo': 'bar', 'baz': 'f oo=bar'},
-            parse_tag_value('   foo  \t= bar;\tbaz=  f oo=bar  '))
-
-    def test_missing_value_is_an_error(self):
-        self.assertRaisesRegexp(
-            InvalidTagSpec, 'baz',
-            parse_tag_value, 'foo=bar;baz')
-
-    def test_duplicate_tag_is_an_error(self):
-        self.assertRaisesRegexp(
-            DuplicateTag, 'foo',
-            parse_tag_value, 'foo=bar;foo=baz')
-
-
 def test_suite():
     from unittest import TestLoader
     return TestLoader().loadTestsFromName(__name__)
diff --git a/dkim/tests/test_util.py b/dkim/tests/test_util.py
new file mode 100644
index 0000000..1ee6ccc
--- /dev/null
+++ b/dkim/tests/test_util.py
@@ -0,0 +1,69 @@
+# This software is provided 'as-is', without any express or implied
+# warranty.  In no event will the author be held liable for any damages
+# arising from the use of this software.
+#
+# Permission is granted to anyone to use this software for any purpose,
+# including commercial applications, and to alter it and redistribute it
+# freely, subject to the following restrictions:
+#
+# 1. The origin of this software must not be misrepresented; you must not
+#    claim that you wrote the original software. If you use this software
+#    in a product, an acknowledgment in the product documentation would be
+#    appreciated but is not required.
+# 2. Altered source versions must be plainly marked as such, and must not be
+#    misrepresented as being the original software.
+# 3. This notice may not be removed or altered from any source distribution.
+#
+# Copyright (c) 2011 William Grant <me@williamgrant.id.au>
+
+import unittest
+
+from dkim.util import (
+    DuplicateTag,
+    InvalidTagSpec,
+    parse_tag_value,
+    )
+
+
+class TestParseTagValue(unittest.TestCase):
+    """Tag=Value parsing tests."""
+
+    def test_single(self):
+        self.assertEqual(
+            {'foo': 'bar'},
+            parse_tag_value('foo=bar'))
+
+    def test_trailing_separator_ignored(self):
+        self.assertEqual(
+            {'foo': 'bar'},
+            parse_tag_value('foo=bar;'))
+
+    def test_multiple(self):
+        self.assertEqual(
+            {'foo': 'bar', 'baz': 'foo'},
+            parse_tag_value('foo=bar;baz=foo'))
+
+    def test_value_with_equals(self):
+        self.assertEqual(
+            {'foo': 'bar', 'baz': 'foo=bar'},
+            parse_tag_value('foo=bar;baz=foo=bar'))
+
+    def test_whitespace_is_stripped(self):
+        self.assertEqual(
+            {'foo': 'bar', 'baz': 'f oo=bar'},
+            parse_tag_value('   foo  \t= bar;\tbaz=  f oo=bar  '))
+
+    def test_missing_value_is_an_error(self):
+        self.assertRaisesRegexp(
+            InvalidTagSpec, 'baz',
+            parse_tag_value, 'foo=bar;baz')
+
+    def test_duplicate_tag_is_an_error(self):
+        self.assertRaisesRegexp(
+            DuplicateTag, 'foo',
+            parse_tag_value, 'foo=bar;foo=baz')
+
+
+def test_suite():
+    from unittest import TestLoader
+    return TestLoader().loadTestsFromName(__name__)