diff --git a/nailgun/api/handlers.py b/nailgun/api/handlers.py
index 958cbc6a4..bbdf38e1b 100644
--- a/nailgun/api/handlers.py
+++ b/nailgun/api/handlers.py
@@ -125,6 +125,7 @@ class ClusterHandler(JSONHandler):
         # /additional validation needed?
         for key, value in data.iteritems():
             if key == "nodes":
+                map(cluster.nodes.remove, cluster.nodes)
                 nodes = web.ctx.orm.query(Node).filter(
                      Node.id.in_(value)
                 )
@@ -366,7 +367,9 @@ class RoleCollectionHandler(JSONHandler):
 
     def GET(self):
         web.header('Content-Type', 'application/json')
-        data = Role.validate_json(web.data())
+        data = web.data() if web.data() else {}
+        if data:
+            data = Role.validate_json(data)
         if 'release_id' in data:
             return json.dumps(map(
                     RoleHandler.render,
diff --git a/nailgun/api/models.py b/nailgun/api/models.py
index 0a18b917f..efdf9fe97 100644
--- a/nailgun/api/models.py
+++ b/nailgun/api/models.py
@@ -167,6 +167,8 @@ class Node(Base, BasicValidator):
         d = cls.validate_json(data)
         if not "mac" in d:
             raise web.webapi.badrequest(message="No mac address specified")
+        if "id" in d:
+            raise web.webapi.badrequest(message="Manual ID setting is prohibited")
         return d
 
     @classmethod
@@ -174,6 +176,8 @@ class Node(Base, BasicValidator):
         d = cls.validate_json(data)
         if "status" in d and d["status"] not in cls.NODE_STATUSES:
             raise web.webapi.badrequest(message="Invalid status for node")
+        if "id" in d:
+            raise web.webapi.badrequest(message="Manual ID setting is prohibited")
         return d
 
 
diff --git a/nailgun/api/validators.py b/nailgun/api/validators.py
index de58c7038..bf49519a2 100644
--- a/nailgun/api/validators.py
+++ b/nailgun/api/validators.py
@@ -12,10 +12,13 @@ class BasicValidator(object):
                 res = json.loads(data)
             except:
                 raise web.webapi.badrequest(
-                    message="Invalid json format!"
+                    message="Invalid json format"
                 )
-            return res
-        return data
+        else:
+            raise web.webapi.badrequest(
+                message="Empty request received"
+            )
+        return res
 
     @classmethod
     def validate(cls, data):