From 1126c9ba4533437ff2a4f163140c9a8e856f6deb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kai=20M=C3=BChlbauer?= <kai.muehlbauer@uni-bonn.de>
Date: Mon, 20 Jan 2025 07:41:05 +0100
Subject: [PATCH] cast type to PDDatetimeUnitOptions (#9963)

---
 xarray/coding/times.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/xarray/coding/times.py b/xarray/coding/times.py
index 0f9a7a48ef8..fd99a55a2a2 100644
--- a/xarray/coding/times.py
+++ b/xarray/coding/times.py
@@ -595,7 +595,9 @@ def _numbers_to_timedelta(
     # estimate fitting resolution for floating point values
     # this iterates until all floats are fractionless or time_unit == "ns"
     if flat_num.dtype.kind == "f" and time_unit != "ns":
-        flat_num, new_time_unit = _check_higher_resolution(flat_num, time_unit)
+        flat_num, new_time_unit = _check_higher_resolution(
+            flat_num, cast(PDDatetimeUnitOptions, time_unit)
+        )
         if time_unit != new_time_unit:
             msg = (
                 f"Can't decode floating point {datatype} to {time_unit!r} without "