diff --git a/matlab/RunOpenEMS.m b/matlab/RunOpenEMS.m
index e6d1ea7..cf3b977 100644
--- a/matlab/RunOpenEMS.m
+++ b/matlab/RunOpenEMS.m
@@ -29,10 +29,14 @@ function RunOpenEMS(Sim_Path, Sim_File, opts, Settings)
 % -----------------------
 % author: Thorsten Liebig
 
-if nargin < 3
+if nargin < 2
     error 'specify the Sim_Path and Sim_file to simulate'
 end
 
+if nargin < 3
+    opts = '';
+end
+
 if (nargin<4)
     Settings = [];
 end