diff --git a/src/toolbox_scs/routines/knife_edge.py b/src/toolbox_scs/routines/knife_edge.py
index 1b22dc8187ba4e5f676a18ee880390d2ba7ba2ef..78ad7d52ca04a565ad846842d6a283f25209d8cc 100644
--- a/src/toolbox_scs/routines/knife_edge.py
+++ b/src/toolbox_scs/routines/knife_edge.py
@@ -15,7 +15,7 @@ __all__ = [
 
 
 def knife_edge(ds, axisKey='scannerX', signalKey='FastADC4peaks',
-               axisRange=[None, None], p0=None, full=False, plot=False,
+               axisRange=None, p0=None, full=False, plot=False,
                display=False):
     """
     Calculates the beam radius at 1/e^2 from a knife-edge scan by