diff --git a/subunit2sql/read_subunit.py b/subunit2sql/read_subunit.py
index 2850283..19e98aa 100644
--- a/subunit2sql/read_subunit.py
+++ b/subunit2sql/read_subunit.py
@@ -37,6 +37,8 @@ class ReadSubunit(object):
                  targets=None):
         if targets is None:
             targets = []
+        else:
+            targets = targets[:]
         self.stream_file = stream_file
         self.stream = subunit.ByteStreamToStreamResult(self.stream_file)
         starts = testtools.StreamResult()
diff --git a/subunit2sql/tests/test_read_subunit.py b/subunit2sql/tests/test_read_subunit.py
index 450264a..70d7547 100644
--- a/subunit2sql/tests/test_read_subunit.py
+++ b/subunit2sql/tests/test_read_subunit.py
@@ -175,3 +175,18 @@ class TestReadSubunit(base.TestCase):
     def test_targets_added_to_result(self, ttc_mock):
         subunit.ReadSubunit(mock.MagicMock(), targets=['foo'])
         self.assertIn('foo', ttc_mock.call_args[0][0])
+
+    @mock.patch('testtools.CopyStreamResult')
+    def test_targets_not_modified(self, ttc_mock):
+        # A regression test that verifies that the subunit reader does
+        # not modify the passed in value of targets.
+        targets = ['foo']
+
+        subunit.ReadSubunit(mock.MagicMock(), targets=targets)
+        ntargets1 = len(ttc_mock.call_args[0][0])
+
+        subunit.ReadSubunit(mock.MagicMock(), targets=targets)
+        ntargets2 = len(ttc_mock.call_args[0][0])
+
+        self.assertEqual(ntargets1, ntargets2)
+        self.assertEqual(targets, ['foo'])