diff --git a/neutron/db/l3_agentschedulers_db.py b/neutron/db/l3_agentschedulers_db.py
index a12f7840f1c..ef951ccd9c9 100644
--- a/neutron/db/l3_agentschedulers_db.py
+++ b/neutron/db/l3_agentschedulers_db.py
@@ -159,33 +159,24 @@ class L3AgentSchedulerDbMixin(l3agentscheduler.L3AgentSchedulerPluginBase,
         """Validate if the router can be correctly assigned to the agent.
 
         :raises: RouterL3AgentMismatch if attempting to assign DVR router
-          to legacy agent, or centralized router to compute's L3 agents.
+          to legacy agent.
         :raises: InvalidL3Agent if attempting to assign router to an
           unsuitable agent (disabled, type != L3, incompatible configuration)
-        :raises: DVRL3CannotAssignToDvrAgent if attempting to assign DVR
-          router from one DVR Agent to another.
+        :raises: DVRL3CannotAssignToDvrAgent if attempting to assign a
+          router to an agent in 'dvr' mode.
         """
         if agent['agent_type'] != constants.AGENT_TYPE_L3:
             raise l3agentscheduler.InvalidL3Agent(id=agent['id'])
 
-        is_distributed = router.get('distributed')
         agent_mode = self._get_agent_mode(agent)
-        router_type = (
-            'distributed' if is_distributed else
-            'centralized')
 
-        is_agent_router_types_incompatible = (
-            agent_mode == constants.L3_AGENT_MODE_DVR and not is_distributed
-            or agent_mode == constants.L3_AGENT_MODE_LEGACY and is_distributed
-        )
-        if is_agent_router_types_incompatible:
+        if agent_mode == constants.L3_AGENT_MODE_DVR:
+            raise l3agentscheduler.DVRL3CannotAssignToDvrAgent()
+
+        if (agent_mode == constants.L3_AGENT_MODE_LEGACY and
+            router.get('distributed')):
             raise l3agentscheduler.RouterL3AgentMismatch(
-                router_type=router_type, router_id=router['id'],
-                agent_mode=agent_mode, agent_id=agent['id'])
-        if agent_mode == constants.L3_AGENT_MODE_DVR and is_distributed:
-            raise l3agentscheduler.DVRL3CannotAssignToDvrAgent(
-                router_type=router_type, router_id=router['id'],
-                agent_id=agent['id'])
+                router_id=router['id'], agent_id=agent['id'])
 
         is_suitable_agent = (
             agentschedulers_db.services_available(agent['admin_state_up']) and
diff --git a/neutron/extensions/l3agentscheduler.py b/neutron/extensions/l3agentscheduler.py
index 1d0974cec3f..39b6cd77a96 100644
--- a/neutron/extensions/l3agentscheduler.py
+++ b/neutron/extensions/l3agentscheduler.py
@@ -169,14 +169,13 @@ class RouterReschedulingFailed(exceptions.Conflict):
 
 
 class RouterL3AgentMismatch(exceptions.Conflict):
-    message = _("Cannot host %(router_type)s router %(router_id)s "
-                "on %(agent_mode)s L3 agent %(agent_id)s.")
+    message = _("Cannot host distributed router %(router_id)s "
+                "on legacy L3 agent %(agent_id)s.")
 
 
 class DVRL3CannotAssignToDvrAgent(exceptions.Conflict):
-    message = _("Not allowed to manually assign a %(router_type)s "
-                "router %(router_id)s from an existing DVR node "
-                "to another L3 agent %(agent_id)s.")
+    message = _("Not allowed to manually assign a router to an "
+                "agent in 'dvr' mode.")
 
 
 class L3AgentSchedulerPluginBase(object):
diff --git a/neutron/tests/unit/scheduler/test_l3_agent_scheduler.py b/neutron/tests/unit/scheduler/test_l3_agent_scheduler.py
index 80a5db52b25..7c74fb8ad8f 100644
--- a/neutron/tests/unit/scheduler/test_l3_agent_scheduler.py
+++ b/neutron/tests/unit/scheduler/test_l3_agent_scheduler.py
@@ -439,7 +439,7 @@ class L3SchedulerTestBaseMixin(object):
         self._register_l3_dvr_agents()
         self._prepare_l3_agent_dvr_move_exceptions(
             agent_id=self.l3_dvr_agent_id,
-            expected_exception=l3agent.RouterL3AgentMismatch)
+            expected_exception=l3agent.DVRL3CannotAssignToDvrAgent)
 
     def test_add_router_to_l3_agent_mismatch_error_dvr_to_dvr(self):
         self._register_l3_dvr_agents()