diff --git a/opmon/cli.py b/opmon/cli.py
index 5cb070b..cebc7e8 100644
--- a/opmon/cli.py
+++ b/opmon/cli.py
@@ -371,7 +371,7 @@ def backfill(
                     continue
 
                 # resolve config by applying platform and custom config specs
-                spec = MonitoringSpec.from_definition_spec(copy.deepcopy(platform_definitions.spec))
+                spec = MonitoringSpec.from_definition_spec(copy.deepcopy(platform_definitions))
                 platform_defaults = ConfigLoader.configs.get_platform_defaults(platform)
                 if platform_defaults is not None:
                     spec.merge(platform_defaults)
@@ -487,13 +487,14 @@ def preview(
     if start_date is None and end_date is None:
         start_date = datetime.today() - timedelta(days=3)
         end_date = datetime.today() - timedelta(days=1)
+        start_date = pytz.utc.localize(start_date)
+        end_date = pytz.utc.localize(end_date)
     elif start_date is None:
         start_date = end_date - timedelta(days=3)
-    else:
+        start_date = pytz.utc.localize(start_date)
+    elif end_date is None:
         end_date = start_date + timedelta(days=3)
-
-    start_date = pytz.utc.localize(start_date)
-    end_date = pytz.utc.localize(end_date)
+        end_date = pytz.utc.localize(end_date)
 
     table = bq_normalize_name(slug)
 
diff --git a/opmon/statistic.py b/opmon/statistic.py
index 11e483a..0c0ea2f 100644
--- a/opmon/statistic.py
+++ b/opmon/statistic.py
@@ -174,7 +174,7 @@ class Percentile(Statistic):
 
     def _scalar_compute(self, metric: Metric):
         return f"""
-            jackknife_percentile_ci(
+            `moz-fx-data-shared-prod.udf_js.bootstrap_percentile_ci`(
                 {self.percentiles},
                 merge_histogram_values(
                     ARRAY_CONCAT_AGG(
@@ -200,7 +200,7 @@ class Percentile(Statistic):
 
     def _histogram_compute(self, metric: Metric):
         return f"""
-            jackknife_percentile_ci(
+            `moz-fx-data-shared-prod.udf_js.bootstrap_percentile_ci`(
                 {self.percentiles},
                 merge_histogram_values(
                     ARRAY_CONCAT_AGG(
diff --git a/setup.py b/setup.py
index ce3a040..cb6c6b7 100644
--- a/setup.py
+++ b/setup.py
@@ -62,7 +62,7 @@ setup(
         "pytz",
         "requests",
         "toml",
-        "mozilla-jetstream-config-parser",
+        "mozilla-metric-config-parser",
     ],
     include_package_data=True,
     tests_require=test_dependencies,