diff --git a/metricflow/plan_conversion/dataflow_to_sql.py b/metricflow/plan_conversion/dataflow_to_sql.py
index 0294e75926..05895e7a81 100644
--- a/metricflow/plan_conversion/dataflow_to_sql.py
+++ b/metricflow/plan_conversion/dataflow_to_sql.py
@@ -53,7 +53,7 @@
 from metricflow.model.semantic_manifest_lookup import SemanticManifestLookup
 from metricflow.plan_conversion.convert_to_sql_plan import ConvertToSqlPlanResult
 from metricflow.plan_conversion.instance_converters import (
-    AddGroupByMetrics,
+    AddGroupByMetric,
     AddLinkToLinkableElements,
     AddMetadata,
     AddMetrics,
@@ -740,7 +740,7 @@ def visit_compute_metrics_node(self, node: ComputeMetricsNode) -> SqlDataSet:
                     metric_subquery_entity_links=entity_instance.spec.entity_links,
                 ),
             )
-            transform_func = AddGroupByMetrics([group_by_metric_instance])
+            transform_func = AddGroupByMetric(group_by_metric_instance)
 
         output_instance_set = output_instance_set.transform(transform_func)
 
diff --git a/metricflow/plan_conversion/instance_converters.py b/metricflow/plan_conversion/instance_converters.py
index e7c4b60a4f..66180b4064 100644
--- a/metricflow/plan_conversion/instance_converters.py
+++ b/metricflow/plan_conversion/instance_converters.py
@@ -745,11 +745,11 @@ def transform(self, instance_set: InstanceSet) -> InstanceSet:  # noqa: D102
         )
 
 
-class AddGroupByMetrics(InstanceSetTransform[InstanceSet]):
+class AddGroupByMetric(InstanceSetTransform[InstanceSet]):
     """Adds the given metric instances to the instance set."""
 
-    def __init__(self, group_by_metric_instances: List[GroupByMetricInstance]) -> None:  # noqa: D107
-        self._group_by_metric_instances = group_by_metric_instances
+    def __init__(self, group_by_metric_instance: GroupByMetricInstance) -> None:  # noqa: D107
+        self._group_by_metric_instance = group_by_metric_instance
 
     def transform(self, instance_set: InstanceSet) -> InstanceSet:  # noqa: D102
         return InstanceSet(
@@ -757,7 +757,7 @@ def transform(self, instance_set: InstanceSet) -> InstanceSet:  # noqa: D102
             dimension_instances=instance_set.dimension_instances,
             time_dimension_instances=instance_set.time_dimension_instances,
             entity_instances=instance_set.entity_instances,
-            group_by_metric_instances=instance_set.group_by_metric_instances + tuple(self._group_by_metric_instances),
+            group_by_metric_instances=instance_set.group_by_metric_instances + (self._group_by_metric_instance,),
             metric_instances=instance_set.metric_instances,
             metadata_instances=instance_set.metadata_instances,
         )