diff --git a/ceilometerclient/exc.py b/ceilometerclient/exc.py
index 3db1c0cf..8d560389 100644
--- a/ceilometerclient/exc.py
+++ b/ceilometerclient/exc.py
@@ -43,15 +43,21 @@ class HTTPException(BaseException):
         self.details = details
 
     def __str__(self):
-        try:
-            data = json.loads(self.details)
-            message = data.get("error_message", {}).get("faultstring")
+        message = ""
+        if self.details:
+            message = self.details
+            try:
+                data = json.loads(self.details)
+                message = data.get("error_message", "")
+                if isinstance(message, dict) and "faultstring" in message:
+                    message = "ERROR %s" % message["faultstring"]
+            except (ValueError, TypeError, AttributeError):
+                pass
+
             if message:
-                return "%s (HTTP %s) ERROR %s" % (
-                    self.__class__.__name__, self.code, message)
-        except (ValueError, TypeError, AttributeError):
-            pass
-        return "%s (HTTP %s)" % (self.__class__.__name__, self.code)
+                message = " %s" % message
+        return "%s (HTTP %s)%s" % (self.__class__.__name__, self.code,
+                                   message)
 
 
 class HTTPMultipleChoices(HTTPException):
@@ -129,5 +135,10 @@ def from_response(response, details=None):
         # it is something unexpected
         raise TypeError("Function 'from_response' expects only response object"
                         " from httplib or requests libraries.")
-    cls = _code_map.get(code, HTTPException)
-    return cls(details)
+    cls = _code_map.get(code)
+    if cls is None:
+        exc = HTTPException(details)
+        exc.code = code
+        return exc
+    else:
+        return cls(details)
diff --git a/ceilometerclient/tests/unit/test_exc.py b/ceilometerclient/tests/unit/test_exc.py
index b0fd1b14..e67cfc8c 100644
--- a/ceilometerclient/tests/unit/test_exc.py
+++ b/ceilometerclient/tests/unit/test_exc.py
@@ -41,7 +41,7 @@ class HTTPExceptionsTest(utils.BaseTestCase):
     def test_str_no_json(self):
         for k, v in HTTPEXCEPTIONS.items():
             exception = v(details="foo")
-            ret_str = k + " (HTTP " + str(exception.code) + ")"
+            ret_str = k + " (HTTP " + str(exception.code) + ") foo"
             self.assertEqual(ret_str, str(exception))
 
     def test_str_no_error_message(self):
@@ -54,13 +54,14 @@ class HTTPExceptionsTest(utils.BaseTestCase):
         for k, v in HTTPEXCEPTIONS.items():
             exception = v(
                 details=json.dumps({"error_message": {"foo": "bar"}}))
-            ret_str = k + " (HTTP " + str(exception.code) + ")"
+            ret_str = (k + " (HTTP " + str(exception.code) + ") " +
+                       str({u'foo': u'bar'}))
             self.assertEqual(ret_str, str(exception))
 
     def test_str_error_message_unknown_format(self):
         for k, v in HTTPEXCEPTIONS.items():
             exception = v(details=json.dumps({"error_message": "oops"}))
-            ret_str = k + " (HTTP " + str(exception.code) + ")"
+            ret_str = k + " (HTTP " + str(exception.code) + ") oops"
             self.assertEqual(ret_str, str(exception))
 
     def test_str_faultstring(self):