diff --git a/staging/src/k8s.io/apiserver/pkg/storage/etcd3/metrics/metrics.go b/staging/src/k8s.io/apiserver/pkg/storage/etcd3/metrics/metrics.go
index 091eef85ab5..ac023d55d8c 100644
--- a/staging/src/k8s.io/apiserver/pkg/storage/etcd3/metrics/metrics.go
+++ b/staging/src/k8s.io/apiserver/pkg/storage/etcd3/metrics/metrics.go
@@ -85,7 +85,7 @@ var (
 		[]string{"endpoint"},
 	)
 	storageSizeDescription   = compbasemetrics.NewDesc("apiserver_storage_size_bytes", "Size of the storage database file physically allocated in bytes.", []string{"cluster"}, nil, compbasemetrics.ALPHA, "")
-	storageMonitor           = &monitorCollector{}
+	storageMonitor           = &monitorCollector{monitorGetter: func() ([]Monitor, error) { return nil, nil }}
 	etcdEventsReceivedCounts = compbasemetrics.NewCounterVec(
 		&compbasemetrics.CounterOpts{
 			Subsystem:      "apiserver",
diff --git a/staging/src/k8s.io/apiserver/pkg/storage/etcd3/metrics/metrics_test.go b/staging/src/k8s.io/apiserver/pkg/storage/etcd3/metrics/metrics_test.go
index 93d15e4af15..6190131f075 100644
--- a/staging/src/k8s.io/apiserver/pkg/storage/etcd3/metrics/metrics_test.go
+++ b/staging/src/k8s.io/apiserver/pkg/storage/etcd3/metrics/metrics_test.go
@@ -17,6 +17,7 @@ limitations under the License.
 package metrics
 
 import (
+	"context"
 	"errors"
 	"strings"
 	"testing"
@@ -179,3 +180,60 @@ etcd_request_errors_total{operation="foo",type="bar"} 1
 		})
 	}
 }
+
+func TestStorageSizeCollector(t *testing.T) {
+	registry := metrics.NewKubeRegistry()
+	registry.CustomMustRegister(storageMonitor)
+
+	testCases := []struct {
+		desc           string
+		getterOverride func() ([]Monitor, error)
+		err            error
+		want           string
+	}{
+		{
+			desc: "fake etcd getter",
+			getterOverride: func() ([]Monitor, error) {
+				return []Monitor{fakeEtcdMonitor{storageSize: 1e9}}, nil
+			},
+			err: nil,
+			want: `# HELP apiserver_storage_size_bytes [ALPHA] Size of the storage database file physically allocated in bytes.
+			# TYPE apiserver_storage_size_bytes gauge
+			apiserver_storage_size_bytes{cluster="etcd-0"} 1e+09
+			`,
+		},
+		{
+			desc:           "getters not configured",
+			getterOverride: nil,
+			err:            nil,
+			want:           ``,
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			defer registry.Reset()
+			if test.getterOverride != nil {
+				oldGetter := storageMonitor.monitorGetter
+				defer SetStorageMonitorGetter(oldGetter)
+				SetStorageMonitorGetter(test.getterOverride)
+			}
+			if err := testutil.GatherAndCompare(registry, strings.NewReader(test.want), "apiserver_storage_size_bytes"); err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+
+}
+
+type fakeEtcdMonitor struct {
+	storageSize int64
+}
+
+func (m fakeEtcdMonitor) Monitor(_ context.Context) (StorageMetrics, error) {
+	return StorageMetrics{Size: m.storageSize}, nil
+}
+
+func (m fakeEtcdMonitor) Close() error {
+	return nil
+}