diff --git a/wf/script.py b/wf/script.py
index 47dc0bb..db78c79 100755
--- a/wf/script.py
+++ b/wf/script.py
@@ -348,15 +348,15 @@ def find_project_by_id(project_data, target_id):  # {{{
 # }}}
 
 
-def show(parent_id, flat=False, filter_all=[], filter_any=[], color="grey"):  # {{{
+def show(parent_id, flat=False, filter_all=None, filter_any=None, color="grey"):  # {{{
     root_data = load_from_storage("root")
     project_data = find_project_by_id(root_data, parent_id)
     project_data = simplify_project(project_data)
     if flat:
         project_data = flatten_project(project_data)
-    if filter_all is not []:
+    if filter_all is not None:
         pass
-    if filter_any is not []:
+    if filter_any is not None:
         project_data = filter_project_any(project_data, filter_any)
     project_data = strip(project_data, r"<a href=\".*\">.*</a>")
     project_data = strip(project_data, r"<time .*</time>")
@@ -386,17 +386,17 @@ def main():  # {{{
 
     subparsers = parser.add_subparsers(dest="command", required=True)
 
-    dump_parser = subparsers.add_parser("dump", help="Dump storage")
+    subparsers.add_parser("dump", help="Dump storage")
 
     inbox_parser = subparsers.add_parser("inbox", help="Inbox commands")
     inbox_parser.add_argument("name", help="Item text", nargs="*")
 
-    vis_parser = subparsers.add_parser("vis", help="Visualisations")
-    active_parser = subparsers.add_parser("active", help="Active projects")
-    hold_parser = subparsers.add_parser("hold", help="Hold projects")
-    sprint_parser = subparsers.add_parser("sprint", help="Sprint goals")
-    today_parser = subparsers.add_parser("today", help="Today's tasks")
-    habits_parser = subparsers.add_parser("habits", help="Habits")
+    subparsers.add_parser("vis", help="Visualisations")
+    subparsers.add_parser("active", help="Active projects")
+    subparsers.add_parser("hold", help="Hold projects")
+    subparsers.add_parser("sprint", help="Sprint goals")
+    subparsers.add_parser("today", help="Today's tasks")
+    subparsers.add_parser("habits", help="Habits")
 
     args = parser.parse_args()