diff --git a/pkg/provider/metric_store.go b/pkg/provider/metric_store.go
index 176eecc..b0d285c 100644
--- a/pkg/provider/metric_store.go
+++ b/pkg/provider/metric_store.go
@@ -17,7 +17,7 @@ import (
 	"k8s.io/metrics/pkg/apis/external_metrics"
 )
 
-// customMetricsStoredMetric is a wrapper around custom_metrics.MetricValue with a TTL used
+// customMetricsStoredMetric is a wrapper around custom_metrics.MetricValue with a metricsTTL used
 // to clean up stale metrics from the customMetricsStore.
 type customMetricsStoredMetric struct {
 	Value  custom_metrics.MetricValue
@@ -37,6 +37,10 @@ type MetricStore struct {
 	sync.RWMutex
 }
 
+var metricsTTL = func() time.Time {
+	return time.Now().UTC().Add(15 * time.Minute)
+}
+
 // NewMetricStore initializes an empty Metrics Store.
 func NewMetricStore() *MetricStore {
 	return &MetricStore{
@@ -77,7 +81,7 @@ func (s *MetricStore) insertCustomMetric(value custom_metrics.MetricValue, label
 	metric := customMetricsStoredMetric{
 		Value:  value,
 		Labels: labels,
-		TTL:    time.Now().UTC().Add(15 * time.Minute), // TODO: make TTL configurable
+		TTL:    metricsTTL(), // TODO: make metricsTTL configurable
 	}
 
 	metrics, ok := s.customMetricsStore[value.MetricName]
@@ -118,7 +122,7 @@ func (s *MetricStore) insertExternalMetric(metric external_metrics.ExternalMetri
 
 	storedMetric := externalMetricsStoredMetric{
 		Value: metric,
-		TTL:   time.Now().UTC().Add(15 * time.Minute), // TODO: make TTL configurable
+		TTL:   metricsTTL(), // TODO: make metricsTTL configurable
 	}
 
 	labelsKey := hashLabelMap(metric.MetricLabels)
@@ -270,7 +274,7 @@ func (s *MetricStore) ListAllExternalMetrics() []provider.ExternalMetricInfo {
 }
 
 // RemoveExpired removes expired metrics from the Metrics Store. A metric is
-// considered expired if its TTL is before time.Now().
+// considered expired if its metricsTTL is before time.Now().
 func (s *MetricStore) RemoveExpired() {
 	s.Lock()
 	defer s.Unlock()
diff --git a/pkg/provider/metrics_store_test.go b/pkg/provider/metrics_store_test.go
index defa2e3..94a5ec9 100644
--- a/pkg/provider/metrics_store_test.go
+++ b/pkg/provider/metrics_store_test.go
@@ -208,8 +208,10 @@ func TestExternalMetricStorage(t *testing.T) {
 func TestMetricsExpiration(t *testing.T) {
 	metricStore := NewMetricStore()
 
-	oldTime := v1.Time{Time: time.Now().UTC().Add(time.Hour * -1)}
-
+	// Override global TTL to test expiration
+	metricsTTL = func() time.Time {
+		return time.Now().UTC().Add(time.Hour * -1)
+	}
 
 	customMetric := collector.CollectedMetric{
 		Type: v2beta1.MetricSourceType("Object"),
@@ -221,20 +223,19 @@ func TestMetricsExpiration(t *testing.T) {
 				Kind:       "Node",
 				APIVersion: "core/v1",
 			},
-			Timestamp:  oldTime,
+			Timestamp: v1.Time{Time: metricsTTL()},
 		},
 	}
 
-	externalMetric := collector.CollectedMetric {
+	externalMetric := collector.CollectedMetric{
 		Type: v2beta1.MetricSourceType("External"),
 		External: external_metrics.ExternalMetricValue{
 			MetricName: "metric-per-unit",
 			Value:      *resource.NewQuantity(0, ""),
-			Timestamp:  oldTime,
+			Timestamp:  v1.Time{Time: metricsTTL()},
 		},
 	}
 
-
 	metricStore.Insert(customMetric)
 	metricStore.Insert(externalMetric)
 	metricStore.RemoveExpired()