diff --git a/wolfsheep.py b/wolfsheep.py
index ff8a831..bbe4fc2 100644
--- a/wolfsheep.py
+++ b/wolfsheep.py
@@ -18,10 +18,11 @@ class Model:
 
 class Simulator:
     invalid_states = [ set({Model.Wolf,Model.Sheep}), set({Model.Sheep, Model.Cabbage}) ]
+    all_entities = set([Model.Man, Model.Wolf, Model.Sheep, Model.Cabbage])
 
     def simulate(self, state, stack=[]):
         stack = stack + [state]
-        if state.right == set([Model.Man,Model.Wolf,Model.Sheep,Model.Cabbage]):
+        if state.right == Simulator.all_entities:
             return stack
 
         nextStates = []
@@ -49,7 +50,7 @@ class Simulator:
 
 if __name__ == "__main__":
     sim = Simulator()
-    result = sim.simulate(Model([Model.Man, Model.Wolf, Model.Sheep, Model.Cabbage],[]))
+    result = sim.simulate(Model(Simulator.all_entities,[]))
     i = 0
     for state in result:
         print("%d: %s" % (i,state.pretty()))