diff --git a/resotocore/resotocore/model/transform_kind_convert.py b/resotocore/resotocore/model/transform_kind_convert.py
index e2299bc66..cda0f2bd4 100644
--- a/resotocore/resotocore/model/transform_kind_convert.py
+++ b/resotocore/resotocore/model/transform_kind_convert.py
@@ -3,13 +3,13 @@
 
 
 def datetime_before_now(duration_string: str) -> str:
-    duration = parse_duration(duration_string)
+    duration = parse_duration(str(duration_string))
     timestamp = utc() - duration
     return utc_str(timestamp)
 
 
 def duration_until_now(at: str) -> str:
-    timestamp = from_utc(at)
+    timestamp = from_utc(str(at))
     duration = utc() - timestamp
     return duration_str(duration, precision=2)
 
diff --git a/resotoshell/resotoshell/__main__.py b/resotoshell/resotoshell/__main__.py
index 868696456..e608e72a3 100644
--- a/resotoshell/resotoshell/__main__.py
+++ b/resotoshell/resotoshell/__main__.py
@@ -209,7 +209,11 @@ def header_value(s: str) -> Tuple[str, str]:
         default=False,
     )
     arg_parser.add_argument(
-        "--add-headers", help="Add a header to all requests. Format: key:value", nargs="*", type=header_value
+        "--add-headers",
+        help="Add a header to all requests. Format: key:value",
+        nargs="*",
+        default=[],
+        type=header_value,
     )