diff --git a/.travis.yml b/.travis.yml
index 711e44c..dd8fcfe 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,6 +4,15 @@ python:
   - "2.7"
   - "3.4"
   - "3.5"
+  - "3.6"
+
+# Python 3.7 requires OpenSSL 1.0.2+, which is only available on Travis
+# via xenial and sudo. Require them for only the build that needs them.
+matrix:
+  include:
+    - python: "3.7"
+      dist: xenial
+      sudo: true
 
 before_script:
   - pip install tox
@@ -12,3 +21,5 @@ script:
   - if [[ $TRAVIS_PYTHON_VERSION = '2.7' ]]; then tox -e py27; fi
   - if [[ $TRAVIS_PYTHON_VERSION = '3.4' ]]; then tox -e py34; fi
   - if [[ $TRAVIS_PYTHON_VERSION = '3.5' ]]; then tox -e py35; fi
+  - if [[ $TRAVIS_PYTHON_VERSION = '3.6' ]]; then tox -e py36; fi
+  - if [[ $TRAVIS_PYTHON_VERSION = '3.7' ]]; then tox -e py37; fi
diff --git a/straitlets/builtin_models.py b/straitlets/builtin_models.py
index c871ba4..7592169 100644
--- a/straitlets/builtin_models.py
+++ b/straitlets/builtin_models.py
@@ -127,7 +127,7 @@ def _password_requires_user(self, proposal):
         return new
 
     hosts = List(
-        trait=Unicode,
+        trait=Unicode(),
         minlen=1,
         help=(
             "List of hosts in the replicaset.  "
diff --git a/straitlets/compat.py b/straitlets/compat.py
index 0108f30..d9a510c 100644
--- a/straitlets/compat.py
+++ b/straitlets/compat.py
@@ -1,9 +1,11 @@
 from six import PY3
 
 if PY3:  # pragma: no cover
+    from inspect import getfullargspec as argspec  # noqa
     long = int
     unicode = str
 else:    # pragma: no cover
+    from inspect import getargspec as argspec  # noqa
     long = long
     unicode = unicode
 
@@ -25,6 +27,7 @@ def ensure_unicode(s, encoding='utf-8'):
 
 
 __all__ = [
+    'argspec',
     'ensure_bytes',
     'ensure_unicode',
     'long',
diff --git a/straitlets/ext/tests/test_click.py b/straitlets/ext/tests/test_click.py
index 0f1e603..74032cd 100644
--- a/straitlets/ext/tests/test_click.py
+++ b/straitlets/ext/tests/test_click.py
@@ -59,9 +59,7 @@ def missing_attr_instance():
 multi_error_output = re.compile(
     dedent(
         """\
-        ^Usage: main \[OPTIONS\]
-
-        Error: Invalid value for "--config": Failed to validate the schema:
+        Failed to validate the schema:
 
         bool:
           No default value found for bool trait of <.+?>
@@ -69,18 +67,16 @@ def missing_attr_instance():
           No default value found for int trait of <.+?>
         unicode:
           No default value found for unicode trait of <.+?>
-        $""",
+        """,
     ),
 )
 
 single_error_output = re.compile(
     dedent(
         """\
-        ^Usage: main \[OPTIONS\]
-
-        Error: Invalid value for "--config": Failed to validate the schema:
+        Failed to validate the schema:
           No default value found for int trait of <.+?>
-        $""",
+        """,
     ),
 )
 
@@ -128,7 +124,7 @@ def main(config):  # pragma: no cover
             catch_exceptions=False,
         )
         assert result.exit_code
-        assert multi_error_output.match(result.output)
+        assert multi_error_output.search(result.output)
 
 
 def test_json_single_error(runner, missing_attr_instance):
@@ -148,7 +144,7 @@ def main(config):  # pragma: no cover
             catch_exceptions=False,
         )
         assert result.exit_code
-        assert single_error_output.match(result.output)
+        assert single_error_output.search(result.output)
 
 
 def test_yaml_file(runner, expected_instance):
@@ -194,7 +190,7 @@ def main(config):  # pragma: no cover
             catch_exceptions=False,
         )
         assert result.exit_code
-        assert multi_error_output.match(result.output)
+        assert multi_error_output.search(result.output)
 
 
 def test_yaml_single_error(runner, missing_attr_instance):
@@ -214,4 +210,4 @@ def main(config):  # pragma: no cover
             catch_exceptions=False,
         )
         assert result.exit_code
-        assert single_error_output.match(result.output)
+        assert single_error_output.search(result.output)
diff --git a/straitlets/tests/test_examples.py b/straitlets/tests/test_examples.py
index eb42432..90acc81 100644
--- a/straitlets/tests/test_examples.py
+++ b/straitlets/tests/test_examples.py
@@ -152,14 +152,14 @@ def test_nested_example():
 
     class C(Serializable):
         point = Instance(Point)
-        unicode_ = Unicode(example='foo')
+        unicode_ = Unicode().tag(example='foo')
 
     class B(Serializable):
-        value = Integer(example=ord('b'))
+        value = Integer().tag(example=ord('b'))
         next_ = Instance(C)
 
     class A(Serializable):
-        value = Integer(example=ord('a'))
+        value = Integer().tag(example=ord('a'))
         next_ = Instance(B)
 
     expected = A(
diff --git a/straitlets/tests/test_serializable.py b/straitlets/tests/test_serializable.py
index 6132447..bb70a6a 100644
--- a/straitlets/tests/test_serializable.py
+++ b/straitlets/tests/test_serializable.py
@@ -109,7 +109,7 @@ class DynamicDefaults(Serializable):
     def _d_default(self):
         return self.DEFAULT_D
 
-    l = List()
+    l = List()  # noqa
     DEFAULT_L = [1, 2, not_ascii, 3]
 
     def _l_default(self):
diff --git a/straitlets/to_primitive.py b/straitlets/to_primitive.py
index f93f757..0de461b 100644
--- a/straitlets/to_primitive.py
+++ b/straitlets/to_primitive.py
@@ -13,6 +13,7 @@ def to_primitive(obj):
         )
     )
 
+
 _base_handler = to_primitive.dispatch(object)
 
 
diff --git a/straitlets/traits.py b/straitlets/traits.py
index ce743ad..e831131 100644
--- a/straitlets/traits.py
+++ b/straitlets/traits.py
@@ -8,10 +8,10 @@
 - More strict handling of default values than traitlets' built-in behavior.
 """
 from contextlib import contextmanager
-import inspect
 
 import traitlets as tr
 
+from . import compat
 from .to_primitive import to_primitive, can_convert_to_primitive
 
 
@@ -97,7 +97,7 @@ def _get_default_value_sentinel(t):
     # signature.
     if t is tr.Tuple:
         return tr.Undefined
-    argspec = inspect.getargspec(t.__init__)
+    argspec = compat.argspec(t.__init__)
     for name, value in zip(reversed(argspec.args), reversed(argspec.defaults)):
         if name == 'default_value':
             return value
@@ -106,6 +106,7 @@ def _get_default_value_sentinel(t):
         "Can't find default value sentinel for type %s" % t
     )
 
+
 _NOTPASSED = object()
 _TRAITLETS_CONTAINER_TYPES = frozenset([tr.List, tr.Set, tr.Dict, tr.Tuple])
 _DEFAULT_VALUE_SENTINELS = {
diff --git a/tox.ini b/tox.ini
index 83d2983..539ce56 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist=py{27,34,35}
+envlist=py{27,34,35,36,37}
 skip_missing_interpreters=True
 
 [testenv]
@@ -10,3 +10,6 @@ commands=
 [pytest]
 addopts = --pep8 --cov straitlets --cov-report term-missing --cov-report html
 testpaths = straitlets
+filterwarnings =
+    # PyYAML==3.13
+    ignore:Using or importing the ABCs:DeprecationWarning:yaml.constructor:126