diff --git a/tempest/common/rest_client.py b/tempest/common/rest_client.py
index 170a137..c582826 100644
--- a/tempest/common/rest_client.py
+++ b/tempest/common/rest_client.py
@@ -338,6 +338,11 @@
             return self.check_over_limit(resp_body, method, url, headers, body,
                                          depth, wait)
 
+        if resp.status == 422:
+            if parse_resp:
+                resp_body = self._parse_resp(resp_body)
+            raise exceptions.UnprocessableEntity(resp_body)
+
         if resp.status in (500, 501):
             message = resp_body
             if parse_resp:
diff --git a/tempest/exceptions.py b/tempest/exceptions.py
index 577aa13..235a2e7 100644
--- a/tempest/exceptions.py
+++ b/tempest/exceptions.py
@@ -94,6 +94,10 @@
     message = "Bad request"
 
 
+class UnprocessableEntity(RestClientException):
+    message = "Unprocessable entity"
+
+
 class AuthenticationFailure(RestClientException):
     message = ("Authentication with user %(user)s and password "
                "%(password)s failed")
diff --git a/tempest/tests/compute/floating_ips/test_floating_ips_actions.py b/tempest/tests/compute/floating_ips/test_floating_ips_actions.py
index d9f9613..0ff81e1 100644
--- a/tempest/tests/compute/floating_ips/test_floating_ips_actions.py
+++ b/tempest/tests/compute/floating_ips/test_floating_ips_actions.py
@@ -162,7 +162,8 @@
                             self.new_server_id)
 
         # Make sure no longer associated with old server
-        self.assertRaises((exceptions.NotFound, exceptions.BadRequest),
+        self.assertRaises((exceptions.NotFound,
+                           exceptions.UnprocessableEntity),
                           self.client.disassociate_floating_ip_from_server,
                           self.floating_ip, self.server_id)