diff -r f0666e56a552 Lib/json/tests/test_unicode.py
--- a/Lib/json/tests/test_unicode.py	Thu Jan 05 23:23:52 2012 -0800
+++ b/Lib/json/tests/test_unicode.py	Thu Jan 12 11:14:01 2012 +0100
@@ -80,6 +80,10 @@
         # Issue 10038.
         self.assertEqual(type(self.loads('"foo"')), unicode)
 
+    def test_bad_encoding(self):
+        self.assertRaises(UnicodeEncodeError, self.loads, '"a"', u"rat\xe9")
+        self.assertRaises(TypeError, self.loads, '"a"', 1)
+
 
 class TestPyUnicode(TestUnicode, PyTest): pass
 class TestCUnicode(TestUnicode, CTest): pass
diff -r f0666e56a552 Modules/_json.c
--- a/Modules/_json.c	Thu Jan 05 23:23:52 2012 -0800
+++ b/Modules/_json.c	Thu Jan 12 11:14:01 2012 +0100
@@ -1725,8 +1725,15 @@
         Py_DECREF(s->encoding);
         s->encoding = tmp;
     }
-    if (s->encoding == NULL || !PyString_Check(s->encoding))
+    if (s->encoding == NULL)
         goto bail;
+    if (!PyString_Check(s->encoding)) {
+	PyErr_Format(PyExc_TypeError,
+		     "encoding must be a string, not %.80s",
+		     Py_TYPE(s->encoding)->tp_name);
+	goto bail;
+    }
+       
 
     /* All of these will fail "gracefully" so we don't need to verify them */
     s->strict = PyObject_GetAttrString(ctx, "strict");