diff --git a/ui/medashare/cli.py b/ui/medashare/cli.py
index ce655e0..d61dad9 100644
--- a/ui/medashare/cli.py
+++ b/ui/medashare/cli.py
@@ -278,6 +278,13 @@ class _JSONEncoder(json.JSONEncoder):
 
 _jsonencoder = _JSONEncoder()
 
+class _TestJSONEncoder(unittest.TestCase):
+	def test_defaultfailure(self):
+		class Foo:
+			pass
+
+		self.assertRaises(TypeError, _jsonencoder.encode, Foo())
+
 class Persona(object):
 	'''The object that represents a persona, or identity.  It will
 	create the proper identity object, serialize for saving keys,
diff --git a/ui/medashare/tests.py b/ui/medashare/tests.py
index 93147be..db68722 100644
--- a/ui/medashare/tests.py
+++ b/ui/medashare/tests.py
@@ -1,3 +1,4 @@
 from .cli import _TestCononicalCoder, _TestCases as cli_test_cases
+from .cli import _TestJSONEncoder
 from .mtree import Test
 from .server import _TestCases, _TestPostConfig