diff --git a/Lib/json/tests/test_unicode.py b/Lib/json/tests/test_unicode.py
--- a/Lib/json/tests/test_unicode.py
+++ b/Lib/json/tests/test_unicode.py
@@ -80,6 +80,17 @@
         # Issue 10038.
         self.assertEqual(type(self.loads('"foo"')), unicode)
 
+    def test_lone_surrogates(self):
+        for surrogate in [0xd800, 0xdbff, 0xdc00, 0xdfff]:
+            ch = unichr(surrogate)
+            with self.assertRaises(UnicodeEncodeError):
+                self.dumps(ch)
+            with self.assertRaises(UnicodeEncodeError):
+                self.dumps(ch.encode('utf-8'))
+            with self.assertRaises(UnicodeDecodeError):
+                self.loads(u'"\\u%04x"' % surrogate)
+            with self.assertRaises(UnicodeDecodeError):
+                self.loads('"\u%04x"' % surrogate)
 
 class TestPyUnicode(TestUnicode, PyTest): pass
 class TestCUnicode(TestUnicode, CTest): pass