diff --git a/CHANGES.txt b/CHANGES.txt
index 3302b3202..d8ddbbe81 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -2,6 +2,9 @@
 Changes for crate
 =================
 
+ - drop server from active list if it responds
+   a valid 50x error and retry with next server
+
  - use bulk_args in executemany to increase performance:
     With crate server >= 0.42.0 executemany uses bulk_args
     and returns a list of results.
diff --git a/src/crate/client/http.py b/src/crate/client/http.py
index 2c2d9811b..bc7b4d9f1 100644
--- a/src/crate/client/http.py
+++ b/src/crate/client/http.py
@@ -288,6 +288,10 @@ def _request(self, method, path, server=None, **kwargs):
                     self._add_server(redirect_server)
                     return self._request(
                         method, path, server=redirect_server, **kwargs)
+                if not server and (500 <= response.status < 600):
+                    with self._lock:
+                        # drop server from active ones
+                        self._drop_server(next_server, response.reason)
                 return response
             except (urllib3.exceptions.MaxRetryError,
                     urllib3.exceptions.ReadTimeoutError,
@@ -295,18 +299,14 @@ def _request(self, method, path, server=None, **kwargs):
                     urllib3.exceptions.HTTPError,
                     urllib3.exceptions.ProxyError,
                    ) as ex:
-                # drop server from active ones
                 ex_message = hasattr(ex, 'message') and ex.message or str(ex)
                 if server:
                     raise ConnectionError(
                         "Server not available, exception: %s" % ex_message
                     )
-                self._drop_server(next_server, ex_message)
-                # if this is the last server raise exception, otherwise try next
-                if not self._active_servers:
-                    raise ConnectionError(
-                        ("No more Servers available, "
-                         "exception from last server: %s") % ex_message)
+                with self._lock:
+                    # drop server from active ones
+                    self._drop_server(next_server, ex_message)
             except Exception as e:
                 ex_message = hasattr(e, 'message') and e.message or str(e)
                 raise ProgrammingError(ex_message)
@@ -409,15 +409,19 @@ def _drop_server(self, server, message):
         """
         Drop server from active list and adds it to the inactive ones.
         """
-        with self._lock:
-            try:
-                self._active_servers.remove(server)
-            except ValueError:
-                pass
-            else:
-                heapq.heappush(self._inactive_servers, (time(), server,
-                                                        message))
-                logger.warning("Removed server %s from active pool", server)
+        try:
+            self._active_servers.remove(server)
+        except ValueError:
+            pass
+        else:
+            heapq.heappush(self._inactive_servers, (time(), server, message))
+            logger.warning("Removed server %s from active pool", server)
+
+        # if this is the last server raise exception, otherwise try next
+        if not self._active_servers:
+            raise ConnectionError(
+                ("No more Servers available, "
+                 "exception from last server: %s") % message)
 
     def _roundrobin(self):
         """
diff --git a/src/crate/client/test_http.py b/src/crate/client/test_http.py
index 34ef66563..312653a5e 100644
--- a/src/crate/client/test_http.py
+++ b/src/crate/client/test_http.py
@@ -84,6 +84,33 @@ class FakeServerServiceUnavailable(FakeServerErrorResponse):
     reason = "Service Unavailable"
 
 
+class FakeServer50xResponse(FakeServerErrorResponse):
+
+    counter = 0
+    STATI = [200, 503]
+    REASONS = ["Success", "Service Unavailable"]
+
+    _status = 200
+    _reason = "Success"
+
+    @property
+    def status(self):
+        return self._status
+
+    @property
+    def reason(self):
+        return self._reason
+
+    def request(self, method, path, data=None, stream=False, **kwargs):
+        self._reason = self.REASONS[self.counter%2]
+        self._status = self.STATI[self.counter%2]
+        self.counter += 1
+        mock_response = MagicMock()
+        mock_response.status = self._status
+        mock_response.reason = self._reason
+        mock_response.headers = {"content-type": self.content_type}
+        return mock_response
+
 class FakeServerUnauthorized(FakeServerErrorResponse):
 
     status = 401
@@ -166,6 +193,17 @@ def test_programming_error_contains_http_error_response_content(self):
         else:
             self.assertTrue(False)
 
+    @patch('crate.client.http.Server', FakeServer50xResponse)
+    def test_server_error_50x(self):
+        client = Client(servers="localhost:4200")
+        client.sql('select 1')
+        try:
+            client.sql('select 2')
+        except ProgrammingError as e:
+            self.assertEqual("No more Servers available, exception from last server: Service Unavailable",
+                             e.message)
+        self.assertEqual([], list(client._active_servers))
+
     def test_connect(self):
         client = Client(servers="localhost:4200 localhost:4201")
         self.assertEqual(client._active_servers,