diff --git a/integration/metrics_test.go b/integration/metrics_test.go
index 91d35ebc2a54..d5961d99a04e 100644
--- a/integration/metrics_test.go
+++ b/integration/metrics_test.go
@@ -15,13 +15,16 @@
 package integration
 
 import (
+	"context"
+	"strconv"
 	"testing"
 
+	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
 	"github.com/coreos/etcd/pkg/testutil"
 )
 
-// TestMetricDbSize checks that the db size metric is set on boot.
-func TestMetricDbSize(t *testing.T) {
+// TestMetricDbSizeBoot checks that the db size metric is set on boot.
+func TestMetricDbSizeBoot(t *testing.T) {
 	defer testutil.AfterTest(t)
 	clus := NewClusterV3(t, &ClusterConfig{Size: 1})
 	defer clus.Terminate(t)
@@ -35,3 +38,57 @@ func TestMetricDbSize(t *testing.T) {
 		t.Fatalf("expected non-zero, got %q", v)
 	}
 }
+
+// TestMetricDbSizeDefrag checks that the db size metric is set after defrag.
+func TestMetricDbSizeDefrag(t *testing.T) {
+	defer testutil.AfterTest(t)
+	clus := NewClusterV3(t, &ClusterConfig{Size: 1})
+	defer clus.Terminate(t)
+
+	kvc := toGRPC(clus.Client(0)).KV
+	mc := toGRPC(clus.Client(0)).Maintenance
+
+	// expand the db size
+	numPuts := 20
+	putreq := &pb.PutRequest{Key: []byte("k"), Value: make([]byte, 4096)}
+	putreq.Value[0] = 1
+	for i := 0; i < numPuts; i++ {
+		if _, err := kvc.Put(context.TODO(), putreq); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	beforeDefrag, err := clus.Members[0].Metric("etcd_debugging_mvcc_db_total_size_in_bytes")
+	if err != nil {
+		t.Fatal(err)
+	}
+	bv, err := strconv.Atoi(beforeDefrag)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if expected := numPuts * len(putreq.Value); bv < expected {
+		t.Fatalf("expected db size greater than %d, got %d", expected, bv)
+	}
+
+	// clear out historical keys
+	creq := &pb.CompactionRequest{Revision: int64(numPuts), Physical: true}
+	if _, err := kvc.Compact(context.TODO(), creq); err != nil {
+		t.Fatal(err)
+	}
+
+	// defrag should give freed space back to fs
+	mc.Defragment(context.TODO(), &pb.DefragmentRequest{})
+	afterDefrag, err := clus.Members[0].Metric("etcd_debugging_mvcc_db_total_size_in_bytes")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	av, err := strconv.Atoi(afterDefrag)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if bv <= av {
+		t.Fatalf("expected less than %d, got %d after defrag", bv, av)
+	}
+}