diff --git a/bob/devtools/scripts/mirror.py b/bob/devtools/scripts/mirror.py
index 0635143b16202fe9c9a3e24121a01a1bbdca87be..14884bb561640d612100c30a14be8afbcb38c3a6 100644
--- a/bob/devtools/scripts/mirror.py
+++ b/bob/devtools/scripts/mirror.py
@@ -183,7 +183,8 @@ def mirror(
                 verbose=False,
             )
 
-    start_date = start_date.date()  # only interested on the day itself
+    if start_date is not None:
+        start_date = start_date.date()  # only interested on the day itself
 
     for arch in DEFAULT_SUBDIRS: