diff --git a/acceptance/bin/setmtime.py b/acceptance/bin/setmtime.py
index 1ec20a031..ae7f6d7c4 100755
--- a/acceptance/bin/setmtime.py
+++ b/acceptance/bin/setmtime.py
@@ -10,7 +10,7 @@ import datetime
 
 timestamp = sys.argv[1]
 ts, ns = timestamp.split(".")
-dt = datetime.datetime.strptime(ts, "%Y-%m-%d %H:%M:%S")
+dt = datetime.datetime.strptime(ts, "%Y-%m-%d %H:%M:%S").replace(tzinfo=datetime.timezone.utc)
 ns = int(ns.ljust(9, "0"))
 ts = int(dt.timestamp()) * 10**9 + ns
 for filename in sys.argv[2:]: