diff --git a/keystone/exception.py b/keystone/exception.py
index 647de99e9a..04475293fa 100644
--- a/keystone/exception.py
+++ b/keystone/exception.py
@@ -15,6 +15,7 @@
 from oslo_log import log
 from oslo_utils import encodeutils
 import six
+from six.moves import http_client
 
 import keystone.conf
 from keystone.i18n import _, _LW
@@ -84,8 +85,8 @@ class ValidationError(Error):
                        " The server could not comply with the request"
                        " since it is either malformed or otherwise"
                        " incorrect. The client is assumed to be in error.")
-    code = 400
-    title = 'Bad Request'
+    code = int(http_client.BAD_REQUEST)
+    title = http_client.responses[http_client.BAD_REQUEST]
 
 
 class URLValidationError(ValidationError):
@@ -129,8 +130,8 @@ class ValidationTimeStampError(Error):
                        " The server could not comply with the request"
                        " since it is either malformed or otherwise"
                        " incorrect. The client is assumed to be in error.")
-    code = 400
-    title = 'Bad Request'
+    code = int(http_client.BAD_REQUEST)
+    title = http_client.responses[http_client.BAD_REQUEST]
 
 
 class InvalidOperatorError(ValidationError):
@@ -144,8 +145,8 @@ class ValidationExpirationError(Error):
                        " The server could not comply with the request"
                        " since it is either malformed or otherwise"
                        " incorrect. The client is assumed to be in error.")
-    code = 400
-    title = 'Bad Request'
+    code = int(http_client.BAD_REQUEST)
+    title = http_client.responses[http_client.BAD_REQUEST]
 
 
 class StringLengthExceeded(ValidationError):
@@ -160,15 +161,15 @@ class ValidationSizeError(Error):
                        " could not comply with the request because"
                        " the attribute size is invalid (too large)."
                        " The client is assumed to be in error.")
-    code = 400
-    title = 'Bad Request'
+    code = int(http_client.BAD_REQUEST)
+    title = http_client.responses[http_client.BAD_REQUEST]
 
 
 class CircularRegionHierarchyError(Error):
     message_format = _("The specified parent region %(parent_region_id)s "
                        "would create a circular region hierarchy.")
-    code = 400
-    title = 'Bad Request'
+    code = int(http_client.BAD_REQUEST)
+    title = http_client.responses[http_client.BAD_REQUEST]
 
 
 class ForbiddenNotSecurity(Error):
@@ -179,8 +180,8 @@ class ForbiddenNotSecurity(Error):
 
     """
 
-    code = 403
-    title = 'Forbidden'
+    code = int(http_client.FORBIDDEN)
+    title = http_client.responses[http_client.FORBIDDEN]
 
 
 class PasswordVerificationError(ForbiddenNotSecurity):
@@ -249,8 +250,8 @@ class SecurityError(Error):
 
 class Unauthorized(SecurityError):
     message_format = _("The request you have made requires authentication.")
-    code = 401
-    title = 'Unauthorized'
+    code = int(http_client.UNAUTHORIZED)
+    title = http_client.responses[http_client.UNAUTHORIZED]
 
 
 class InsufficientAuthMethods(Error):
@@ -302,8 +303,8 @@ class AdditionalAuthRequired(AuthPluginException):
 class Forbidden(SecurityError):
     message_format = _("You are not authorized to perform the"
                        " requested action.")
-    code = 403
-    title = 'Forbidden'
+    code = int(http_client.FORBIDDEN)
+    title = http_client.responses[http_client.FORBIDDEN]
 
 
 class ForbiddenAction(Forbidden):
@@ -330,8 +331,8 @@ class InvalidDomainConfig(Forbidden):
 
 class NotFound(Error):
     message_format = _("Could not find: %(target)s.")
-    code = 404
-    title = 'Not Found'
+    code = int(http_client.NOT_FOUND)
+    title = http_client.responses[http_client.NOT_FOUND]
 
 
 class EndpointNotFound(NotFound):
@@ -460,8 +461,8 @@ class ConfigRegistrationNotFound(Exception):
 class Conflict(Error):
     message_format = _("Conflict occurred attempting to store %(type)s -"
                        " %(details)s.")
-    code = 409
-    title = 'Conflict'
+    code = int(http_client.CONFLICT)
+    title = http_client.responses[http_client.CONFLICT]
 
 
 class UnexpectedError(SecurityError):
@@ -483,8 +484,8 @@ class UnexpectedError(SecurityError):
         return super(UnexpectedError, self)._build_message(
             message or self.debug_message_format, **kwargs)
 
-    code = 500
-    title = 'Internal Server Error'
+    code = int(http_client.INTERNAL_SERVER_ERROR)
+    title = http_client.responses[http_client.INTERNAL_SERVER_ERROR]
 
 
 class TrustConsumeMaximumAttempt(UnexpectedError):
@@ -528,15 +529,15 @@ class AssignmentTypeCalculationError(UnexpectedError):
 class NotImplemented(Error):
     message_format = _("The action you have requested has not"
                        " been implemented.")
-    code = 501
-    title = 'Not Implemented'
+    code = int(http_client.NOT_IMPLEMENTED)
+    title = http_client.responses[http_client.NOT_IMPLEMENTED]
 
 
 class Gone(Error):
     message_format = _("The service you have requested is no"
                        " longer available on this server.")
-    code = 410
-    title = 'Gone'
+    code = int(http_client.GONE)
+    title = http_client.responses[http_client.GONE]
 
 
 class ConfigFileNotFound(UnexpectedError):