diff --git a/tests/perf/auto_perf_sheriffing/test_backfill_reports/conftest.py b/tests/perf/auto_perf_sheriffing/test_backfill_reports/conftest.py
index eea11dc2f..e1711c6fd 100644
--- a/tests/perf/auto_perf_sheriffing/test_backfill_reports/conftest.py
+++ b/tests/perf/auto_perf_sheriffing/test_backfill_reports/conftest.py
@@ -147,6 +147,15 @@ def test_few_various_alerts():
     return alerts
 
 
+@pytest.fixture
+def test_macosx_alert():
+    alert = Mock(spec=PerformanceAlert)
+    platform = 'macosx1015-64-shippable-qr'
+    alert.series_signature.platform.platform = platform
+    alert.is_regression = True
+    return alert
+
+
 @pytest.fixture
 def test_few_regressions():
     alerts = [Mock(spec=PerformanceAlert) for _ in range(5)]
diff --git a/tests/perf/auto_perf_sheriffing/test_backfill_reports/test_alerts_picker.py b/tests/perf/auto_perf_sheriffing/test_backfill_reports/test_alerts_picker.py
index b311a384c..3242b4c01 100644
--- a/tests/perf/auto_perf_sheriffing/test_backfill_reports/test_alerts_picker.py
+++ b/tests/perf/auto_perf_sheriffing/test_backfill_reports/test_alerts_picker.py
@@ -140,13 +140,16 @@ def test_os_relevance():
     assert 4 == picker._os_relevance('windows7')
     assert 3 == picker._os_relevance('linux')
     assert 2 == picker._os_relevance('osx')
+    assert 2 == picker._os_relevance('macosx')  # ensure macosx has the same relevance as osx
     assert 1 == picker._os_relevance('android')
 
     with pytest.raises(ValueError):
         picker._os_relevance('some weird OS')
 
 
-def test_has_relevant_platform(test_many_various_alerts, test_bad_platform_names):
+def test_has_relevant_platform(
+    test_many_various_alerts, test_bad_platform_names, test_macosx_alert
+):
     picker = AlertsPicker(
         max_alerts=5,
         max_improvements=2,
@@ -157,6 +160,7 @@ def test_has_relevant_platform(test_many_various_alerts, test_bad_platform_names
         assert picker._has_relevant_platform(alert) is True
     for alert in test_bad_platform_names:
         assert picker._has_relevant_platform(alert) is False
+    assert picker._has_relevant_platform(test_macosx_alert) is True
 
 
 def test_extract_by_relevant_platforms(test_many_various_alerts, test_bad_platform_names):
diff --git a/treeherder/perf/auto_perf_sheriffing/backfill_reports.py b/treeherder/perf/auto_perf_sheriffing/backfill_reports.py
index 3b83636f3..1685744eb 100644
--- a/treeherder/perf/auto_perf_sheriffing/backfill_reports.py
+++ b/treeherder/perf/auto_perf_sheriffing/backfill_reports.py
@@ -136,7 +136,7 @@ class AlertsPicker:
         :return: int value of platform's relevance
         """
         for platform_of_interest in self.ordered_platforms_of_interest:
-            if alert_platform.startswith(platform_of_interest):
+            if platform_of_interest in alert_platform:
                 return len(
                     self.ordered_platforms_of_interest
                 ) - self.ordered_platforms_of_interest.index(platform_of_interest)
@@ -148,7 +148,7 @@ class AlertsPicker:
         """
         alert_platform_name = alert.series_signature.platform.platform
         return any(
-            alert_platform_name.startswith(platform_of_interest)
+            platform_of_interest in alert_platform_name
             for platform_of_interest in self.ordered_platforms_of_interest
         )