diff --git a/nailgun/nailgun/api/v1/validators/deployment_graph.py b/nailgun/nailgun/api/v1/validators/deployment_graph.py
index 3b0b3bf4f4..676fd7b23b 100644
--- a/nailgun/nailgun/api/v1/validators/deployment_graph.py
+++ b/nailgun/nailgun/api/v1/validators/deployment_graph.py
@@ -45,9 +45,10 @@ class GraphExecuteParamsValidator(BasicValidator):
 
         nodes_to_check = set()
         for graph in parsed['graphs']:
-            nodes_to_check.update(graph.get('nodes', []))
+            nodes_to_check.update(graph.get('nodes') or [])
 
-        cls.validate_nodes(nodes_to_check, parsed['cluster'])
+        if nodes_to_check:
+            cls.validate_nodes(nodes_to_check, parsed['cluster'])
         return parsed
 
     @classmethod