diff --git a/normalisename.py b/normalisename.py
index 25c0b73..7bc7e81 100755
--- a/normalisename.py
+++ b/normalisename.py
@@ -1,18 +1,24 @@
 #!/usr/bin/env python3
-from sys import argv
 from unidecode import unidecode
 from os import rename
 from os.path import basename, dirname
 from os.path import join as joinpath
+from argparse import ArgumentParser
+
+parser = ArgumentParser(description='Eliminate funky stuff from filenames.')
+parser.add_argument('--separator', '-s', type=str, nargs='?', default='_',
+                    help='Set separator to use (to replace spaces with).')
+parser.add_argument('files', type=str, nargs='+',
+                    help='File(s) to normalise the name of (relative or absolute path).')
+
+args = parser.parse_args()
 
 
-# whitespaces will be replaced
-# dots are ok
-# do not ruin previous work
-# dashes are ok
-whitelist = (' ', '.', '_', '-')
+# special characters that will not be removed
+whitelist = {' ', '.', '-'}
+whitelist.add(args.separator)
 
-for path in argv[1:]:
+for path in args.files:
     dir = dirname(path)
     file = basename(path)
     rename(path,
@@ -21,7 +27,7 @@ for path in argv[1:]:
                joinpath
                (
                    dir,
-                   ''.join(ch for ch in file.replace(' ', '_')
+                   ''.join(ch for ch in file.replace(' ', args.separator)
                            if ch.isalnum()
                            or ch in whitelist)
                )