diff --git a/script/test/TestWaveform.py b/script/test/TestWaveform.py
index d8f8f49e..63e97b7c 100644
--- a/script/test/TestWaveform.py
+++ b/script/test/TestWaveform.py
@@ -1,6 +1,6 @@
 import ch.psi.pshell.epics.ChannelDoubleArray as ChannelDoubleArray
 
-c=ChannelDoubleArray("test", "X03DA-SCIENTA:image1:ArrayData", 3, -1, False)
+c=ChannelDoubleArray("test", "X03DA-SCIENTA:image1:ArrayData", 3, 100, True)
 c.monitored=True
 add_device(c, True)