diff --git a/mlflow/utils/proto_json_utils.py b/mlflow/utils/proto_json_utils.py
index 65fb652a75009..15d7ec5e7f171 100644
--- a/mlflow/utils/proto_json_utils.py
+++ b/mlflow/utils/proto_json_utils.py
@@ -143,7 +143,8 @@ def milliseconds_to_proto_timestamp(milliseconds: int) -> str:
     Converts milliseconds to a timestamp string (e.g. "2025-04-15T08:49:18.699Z").
     """
     t = Timestamp()
-    t.FromMilliseconds(milliseconds)
+    t.seconds = milliseconds // 1000
+    t.nanos = (milliseconds % 1000) * 1_000_000
     return t.ToJsonString()