diff --git a/pyproject.toml b/pyproject.toml
index 07e1c0cc6fce7d..c4a4e904f8375f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -390,7 +390,6 @@ module = [
     "sentry.api.endpoints.organization_releases",
     "sentry.db.postgres.base",
     "sentry.middleware.ratelimit",
-    "sentry.release_health.metrics_sessions_v2",
     "sentry.search.events.builder.errors",
     "sentry.search.events.builder.metrics",
     "sentry.search.events.datasets.filter_aliases",
diff --git a/src/sentry/release_health/metrics_sessions_v2.py b/src/sentry/release_health/metrics_sessions_v2.py
index 790f24bd409d40..12961be5fd00af 100644
--- a/src/sentry/release_health/metrics_sessions_v2.py
+++ b/src/sentry/release_health/metrics_sessions_v2.py
@@ -45,7 +45,10 @@
     MetricGroupByField,
     MetricOrderByField,
 )
-from sentry.snuba.metrics.utils import OrderByNotSupportedOverCompositeEntityException
+from sentry.snuba.metrics.utils import (
+    MetricOperationType,
+    OrderByNotSupportedOverCompositeEntityException,
+)
 from sentry.snuba.sessions_v2 import (
     QueryDefinition,
     finite_or_none,
@@ -302,8 +305,10 @@ def __init__(
 
 
 class DurationField(Field):
+    op: MetricOperationType
+
     def __init__(self, name: str, raw_groupby: Sequence[str], status_filter: StatusFilter):
-        self.op = name[:3]  # That this works is just a lucky coincidence
+        self.op = cast(MetricOperationType, name.split("(", 1)[0])
         super().__init__(name, raw_groupby, status_filter)
 
     def _get_session_status(self, metric_field: MetricField) -> SessionStatus | None: