diff --git a/script/test/psss.py b/script/test/psss.py
index 9ddbe86..f821115 100644
--- a/script/test/psss.py
+++ b/script/test/psss.py
@@ -2,6 +2,7 @@ import ch.psi.pshell.epics.CAS as CAS
 import ch.psi.pshell.device.Register.RegisterArray as RegisterArray
 
 camera = "SLG-LCAM-C102"
+SPECTRUM_SIZE = 659
 
 class Scalar(RegisterBase):    
     def __init__(self, name):
@@ -38,11 +39,11 @@ add_device(Scalar("smax"), True)
 
 
 a,b=[],[]
-for i in range(659):
+for i in range(SPECTRUM_SIZE):
     a.append(i)
     b.append(0)
 sx.write(a)
-sx.write(b)
+sy.write(b)
 cas1 = CAS(camera + ":SPECTRUM_Y", sy, 'double') 
 cas6 = CAS(camera + ":SPECTRUM_X", sx, 'double')
 cas2 = CAS(camera + ":SPECTRUM_CENTER", sc, 'double')