@@ -69,13 +69,13 @@ def to_proto(self) -> AggregationProto:
     @classmethod
     def from_proto(cls, agg_proto: AggregationProto):
         time_window = (
-            None
+            timedelta(days=0)
             if agg_proto.time_window.ToNanoseconds() == 0
             else agg_proto.time_window.ToTimedelta()
         )
 
         slide_interval = (
-            None
+            timedelta(days=0)
             if agg_proto.slide_interval.ToNanoseconds() == 0
             else agg_proto.slide_interval.ToTimedelta()
         )
 
@@ -21,7 +21,7 @@
 import pytest
 
 from feast import Entity, Field
-from feast.aggregation import Aggregation, aggregation_specs_to_agg_ops
+from feast.aggregation import Aggregation
 from feast.on_demand_feature_view import OnDemandFeatureView, on_demand_feature_view
 from feast.types import Float64, Int64
 from feast.value_type import ValueType
@@ -165,26 +165,3 @@ def dummy(df):
             schema=[Field(name="out", dtype=Float64)],
             udf=dummy,
         )
-
-
-def test_aggregation_from_proto_no_time_window_roundtrip():
-    """Aggregation.from_proto preserves None time_window (fixes timedelta(0) regression)."""
-    agg = Aggregation(column="amount", function="sum", name="total_amount")
-    assert agg.time_window is None
-
-    restored = Aggregation.from_proto(agg.to_proto())
-    assert restored.time_window is None
-    assert restored == agg
-
-
-def test_aggregation_from_proto_no_time_window_online_serving():
-    """Aggregations without time_window don't raise in aggregation_specs_to_agg_ops after roundtrip."""
-    agg = Aggregation(column="amount", function="sum", name="total_amount")
-    restored = Aggregation.from_proto(agg.to_proto())
-
-    # Should not raise — time_window is None, not timedelta(0)
-    result = aggregation_specs_to_agg_ops(
-        [restored],
-        time_window_unsupported_error_message="Time window aggregation is not supported in online serving",
-    )
-    assert result == {"total_amount": ("sum", "amount")}