diff --git a/cproxy.c b/cproxy.c
index e6f1fd1c..c0dbe2db 100644
--- a/cproxy.c
+++ b/cproxy.c
@@ -1968,6 +1968,13 @@ void upstream_error_msg(conn *uc, char *ascii_msg,
             binary_status = PROTOCOL_BINARY_RESPONSE_EINTERNAL;
         }
 
+        pthread_mutex_lock(&ptd->proxy->proxy_lock);
+        if (ptd->proxy->name != NULL &&
+            strcmp(ptd->proxy->name, NULL_BUCKET) == 0) {
+            binary_status = PROTOCOL_BINARY_RESPONSE_AUTH_ERROR;
+        }
+        pthread_mutex_unlock(&ptd->proxy->proxy_lock);
+
         write_bin_error(uc, binary_status, 0);
 
         update_event(uc, EV_WRITE | EV_PERSIST);
diff --git a/t/moxi_multitenancy.py b/t/moxi_multitenancy.py
index 1be23e81..3e8097f3 100644
--- a/t/moxi_multitenancy.py
+++ b/t/moxi_multitenancy.py
@@ -61,17 +61,17 @@ def testNullBucket(self):
         """Test null bucket"""
         self.client_connect()
 
-        get_oom = self.packRes(memcacheConstants.CMD_GETK,
-                               status=memcacheConstants.ERR_ENOMEM,
-                               val="Out of memory")
+        get_err = self.packRes(memcacheConstants.CMD_GETK,
+                               status=memcacheConstants.ERR_AUTH_ERROR,
+                               val="Auth failure")
 
         get_req = self.packReq(memcacheConstants.CMD_GETK, key='keyNotThere0')
         self.client_send(get_req)
-        self.client_recv(get_oom)
+        self.client_recv(get_err)
 
         get_req = self.packReq(memcacheConstants.CMD_GETK, key='keyNotThere0')
         self.client_send(get_req)
-        self.client_recv(get_oom)
+        self.client_recv(get_err)
 
         self.assertTrue(self.mock_quiet())
 
@@ -82,15 +82,15 @@ def testNullBucketSet(self):
         set_req = self.packReq(memcacheConstants.CMD_SET, key='simpleSet',
                                extraHeader=struct.pack(memcacheConstants.SET_PKT_FMT, 0, 0),
                                val='123')
-        set_oom = self.packRes(memcacheConstants.CMD_SET,
-                               status=memcacheConstants.ERR_ENOMEM,
-                               val="Out of memory")
+        set_err = self.packRes(memcacheConstants.CMD_SET,
+                               status=memcacheConstants.ERR_AUTH_ERROR,
+                               val="Auth failure")
 
         self.client_send(set_req)
-        self.client_recv(set_oom)
+        self.client_recv(set_err)
 
         self.client_send(set_req)
-        self.client_recv(set_oom)
+        self.client_recv(set_err)
 
         self.assertTrue(self.mock_quiet())