diff --git a/script/RobotSC.py b/script/RobotSC.py
index 2737823..5e04f2b 100644
--- a/script/RobotSC.py
+++ b/script/RobotSC.py
@@ -46,10 +46,10 @@ class jfc(ReadonlyRegisterBase):
     def doRead(self):
         if robot.joint_forces == None:
             print "*",
-            return  None 
+            return   float('NaN')  
         if robot.powered == False:
             print ".",
-            return None
+            return  float('NaN') 
         print "!",
         return (robot.joint_forces[1]+74)/4  + (robot.joint_forces[2]+30)/4 + (robot.joint_forces[4]-0.8)/0.2