diff --git a/merge_images b/merge_images
index c503a29..7b8a2d3 100755
--- a/merge_images
+++ b/merge_images
@@ -12,6 +12,7 @@ Author: Stephan Porada <sporada@uni-bielefeld.de>
 
 import os
 import argparse
+import subprocess
 
 
 def parse_arguments():
@@ -23,11 +24,9 @@ def parse_arguments():
 
 
 def merge_images(input_dir, output_dir):
-    os.system('mkdir {}'.format(output_dir))
-    os.system('ls -v {}/*.* >> file_list.txt'.format(input_dir))
-    os.system('convert @file_list.txt {}/combined.tiff'.format(output_dir))
-    os.system('cat "file_list.txt" | xargs rm')
-    os.system('rm file_list.txt')
+    os.makedirs(output_dir, exist_ok=True)
+    os.system('ls -v {i}/*.* >> {i}file_list.txt'.format(i=input_dir))
+    os.system('convert @{i}/file_list.txt {o}/combined.tiff'.format(i=input_dir, o=output_dir))
 
 
 def main():