diff --git a/python/obitools3/apps/optiongroups/__init__.py b/python/obitools3/apps/optiongroups/__init__.py
index 63cdfbb..ba2c324 100755
--- a/python/obitools3/apps/optiongroups/__init__.py
+++ b/python/obitools3/apps/optiongroups/__init__.py
@@ -1,3 +1,9 @@
+import codecs
+
+def unescaped_str(arg_str):
+    return arg_str.encode('latin-1', 'backslashreplace').decode('unicode-escape')
+
+
 def __addInputOption(optionManager):
     
     optionManager.add_argument(
@@ -133,7 +139,7 @@ def __addTabularOption(optionManager):
     group.add_argument('--sep',
                      action="store", dest="obi:sep",
                      default="\t",
-                     type=str,
+                     type=unescaped_str,
                      help="Column separator")