diff --git a/wsme/rest/json.py b/wsme/rest/json.py
index 77277ce..42a9559 100644
--- a/wsme/rest/json.py
+++ b/wsme/rest/json.py
@@ -166,9 +166,10 @@ def dict_fromjson(datatype, value):
 
 @fromjson.when_object(six.binary_type)
 def str_fromjson(datatype, value):
-    if value is None:
-        return None
-    return value.encode('utf8')
+    if (isinstance(value, six.string_types)
+            or isinstance(value, six.integer_types)
+            or isinstance(value, float)):
+        return six.text_type(value).encode('utf8')
 
 
 @fromjson.when_object(wsme.types.text)
diff --git a/wsme/tests/test_api.py b/wsme/tests/test_api.py
index f08b74b..008a928 100644
--- a/wsme/tests/test_api.py
+++ b/wsme/tests/test_api.py
@@ -86,6 +86,30 @@ Invalid value (should be one of:"))
         self.assertIn('None', res.json_body['faultstring'])
         self.assertEqual(res.status_int, 400)
 
+    def test_validate_enum_with_wrong_type(self):
+        class Version(object):
+            number = types.Enum(str, 'v1', 'v2', None)
+
+        class MyWS(WSRoot):
+            @expose(str)
+            @validate(Version)
+            def setcplx(self, version):
+                pass
+
+        r = MyWS(['restjson'])
+        app = webtest.TestApp(r.wsgiapp())
+        res = app.post_json('/setcplx', params={'version': {'number': 1}},
+                            expect_errors=True,
+                            headers={'Accept': 'application/json'})
+        self.assertTrue(
+            res.json_body['faultstring'].startswith(
+                "Invalid input for field/attribute number. Value: '1'. \
+Invalid value (should be one of:"))
+        self.assertIn('v1', res.json_body['faultstring'])
+        self.assertIn('v2', res.json_body['faultstring'])
+        self.assertIn('None', res.json_body['faultstring'])
+        self.assertEqual(res.status_int, 400)
+
     def test_scan_api(self):
         class NS(object):
             @expose(int)