diff --git a/gprMax/input_cmds_multiuse.py b/gprMax/input_cmds_multiuse.py
index 30655987..e2199df9 100644
--- a/gprMax/input_cmds_multiuse.py
+++ b/gprMax/input_cmds_multiuse.py
@@ -702,7 +702,7 @@ def process_multicmds(multicmds, G):
             if float(tmp[2]) < 0 or float(tmp[3]) < 0 or float(tmp[6]) < 0 or float(tmp[7]) < 0 or float(tmp[10]) < 0:
                 raise CmdInputError("'" + cmdname + ': ' + ' '.join(tmp) + "'" + ' minimum and maximum scaling values must be greater than zero')
             if float(tmp[6]) < 1:
-                raise CmdInputError("'" + cmdname + ': ' + ' '.join(tmp) + "'" + ' minimum scaling value for kappa must be greater than zero')
+                raise CmdInputError("'" + cmdname + ': ' + ' '.join(tmp) + "'" + ' minimum scaling value for kappa must be greater than or equal to one')
 
             cfsalpha = CFSParameter()
             cfsalpha.ID = 'alpha'