diff --git a/script/users/PhotonEnergyManipulator.py b/script/users/PhotonEnergyManipulator.py
index e8527d1b..aaafc88b 100644
--- a/script/users/PhotonEnergyManipulator.py
+++ b/script/users/PhotonEnergyManipulator.py
@@ -37,7 +37,7 @@ MANIP_END = 116.6
 
 ### do not edit below
 
-NSTEPS = round((EPHOT_HI - EPHOT_LO) / EPHOT_STEP) + 1
+NSTEPS = int(round((EPHOT_HI - EPHOT_LO) / EPHOT_STEP) + 1)
 EPHOT_STEP = (EPHOT_HI - EPHOT_LO) / (NSTEPS - 1)
 
 ephot = [EPHOT_LO + EPHOT_STEP * i for i in range(NSTEPS)]