diff --git a/dbt_semantic_interfaces/transformations/cumulative_type_params.py b/dbt_semantic_interfaces/transformations/cumulative_type_params.py
index ae47f5e2..32253969 100644
--- a/dbt_semantic_interfaces/transformations/cumulative_type_params.py
+++ b/dbt_semantic_interfaces/transformations/cumulative_type_params.py
@@ -1,3 +1,5 @@
+from typing import Optional
+
 from typing_extensions import override
 
 from dbt_semantic_interfaces.implementations.metric import PydanticCumulativeTypeParams
@@ -27,7 +29,7 @@ def _implements_protocol(self) -> SemanticManifestTransformRule[PydanticSemantic
         return self
 
     @staticmethod
-    def transform_model(semantic_manifest: PydanticSemanticManifest) -> PydanticSemanticManifest:
+    def transform_model(semantic_manifest: PydanticSemanticManifest) -> PydanticSemanticManifest:  # noqa: D
         for metric in semantic_manifest.metrics:
             if metric.type == MetricType.CUMULATIVE:
                 if not metric.type_params.cumulative_type_params:
@@ -36,11 +38,20 @@ def transform_model(semantic_manifest: PydanticSemanticManifest) -> PydanticSema
                 if metric.type_params.window and not metric.type_params.cumulative_type_params.window:
                     metric.type_params.cumulative_type_params.window = metric.type_params.window
 
-                # Since grain_to_date is just a string, we can't add custom parsing to them. Instead, lowercase them here.
-                if metric.type_params.grain_to_date or metric.type_params.cumulative_type_params.grain_to_date:
-                    metric.type_params.cumulative_type_params.grain_to_date = (
-                        metric.type_params.cumulative_type_params.grain_to_date
-                        or metric.type_params.grain_to_date.value
-                    ).lower()
+                # Since grain_to_date is a string, we can't add custom parsing to it. Instead, lowercase it here.
+                if metric.type_params.grain_to_date or (
+                    metric.type_params.cumulative_type_params
+                    and metric.type_params.cumulative_type_params.grain_to_date
+                ):
+                    grain_to_date: Optional[str] = None
+                    if (
+                        metric.type_params.cumulative_type_params
+                        and metric.type_params.cumulative_type_params.grain_to_date
+                    ):
+                        grain_to_date = metric.type_params.cumulative_type_params.grain_to_date
+                    elif metric.type_params.grain_to_date:
+                        grain_to_date = metric.type_params.grain_to_date.value
+                    if grain_to_date:
+                        metric.type_params.cumulative_type_params.grain_to_date = grain_to_date.lower()
 
         return semantic_manifest
diff --git a/tests/parsing/test_metric_parsing.py b/tests/parsing/test_metric_parsing.py
index b29329a5..af44915f 100644
--- a/tests/parsing/test_metric_parsing.py
+++ b/tests/parsing/test_metric_parsing.py
@@ -12,9 +12,10 @@
 from dbt_semantic_interfaces.parsing.dir_to_model import (
     parse_yaml_files_to_semantic_manifest,
 )
-from dbt_semantic_interfaces.transformations.semantic_manifest_transformer import PydanticSemanticManifestTransformer
-
 from dbt_semantic_interfaces.parsing.objects import YamlConfigFile
+from dbt_semantic_interfaces.transformations.semantic_manifest_transformer import (
+    PydanticSemanticManifestTransformer,
+)
 from dbt_semantic_interfaces.type_enums import (
     ConversionCalculationType,
     MetricType,
@@ -244,8 +245,10 @@ def test_cumulative_window_metric_parsing() -> None:
         assert metric.name == "cumulative_test"
         assert metric.type is MetricType.CUMULATIVE
         assert metric.type_params.measure == PydanticMetricInputMeasure(name="cumulative_measure")
-        assert metric.type_params.cumulative_type_params.window == PydanticMetricTimeWindow(
-            count=7, granularity=TimeGranularity.DAY.value
+        assert (
+            metric.type_params.cumulative_type_params
+            and metric.type_params.cumulative_type_params.window
+            == PydanticMetricTimeWindow(count=7, granularity=TimeGranularity.DAY.value)
         )
 
 
@@ -291,7 +294,10 @@ def test_grain_to_date_metric_parsing() -> None:
         assert metric.type is MetricType.CUMULATIVE
         assert metric.type_params.measure == PydanticMetricInputMeasure(name="cumulative_measure")
         assert metric.type_params.window is None
-        assert metric.type_params.cumulative_type_params.grain_to_date == TimeGranularity.WEEK.value
+        assert (
+            metric.type_params.cumulative_type_params
+            and metric.type_params.cumulative_type_params.grain_to_date == TimeGranularity.WEEK.value
+        )
 
 
 def test_derived_metric_offset_window_parsing() -> None: