diff --git a/storage/index_test.go b/storage/index_test.go
index 88255b950..92f179d97 100644
--- a/storage/index_test.go
+++ b/storage/index_test.go
@@ -91,14 +91,10 @@ func TestIndexTombstone(t *testing.T) {
 	if err != nil {
 		t.Errorf("tombstone error = %v, want nil", err)
 	}
-	rev, _, _, err := index.Get([]byte("foo"), 7)
-	if err != nil {
+	_, _, _, err = index.Get([]byte("foo"), 7)
+	if err != ErrRevisionNotFound {
 		t.Errorf("get error = %v, want nil", err)
 	}
-	w := revision{main: 7}
-	if !reflect.DeepEqual(rev, w) {
-		t.Errorf("get revision = %+v, want %+v", rev, w)
-	}
 }
 
 func TestContinuousCompact(t *testing.T) {
diff --git a/storage/key_index.go b/storage/key_index.go
index 180b607c0..65f70269a 100644
--- a/storage/key_index.go
+++ b/storage/key_index.go
@@ -144,18 +144,14 @@ func (ki *keyIndex) compact(atRev int64, available map[revision]struct{}) {
 		return true
 	}
 
-	g := ki.findGeneration(atRev)
-	if g == nil {
-		return
-	}
-
-	i := 0
-	for i <= len(ki.generations)-1 {
-		wg := &ki.generations[i]
-		if wg == g {
+	i, g := 0, &ki.generations[0]
+	// find first generation includes atRev or created after atRev
+	for i < len(ki.generations)-1 {
+		if tomb := g.revs[len(g.revs)-1].main; tomb > atRev {
 			break
 		}
 		i++
+		g = &ki.generations[i]
 	}
 
 	if !g.isEmpty() {
@@ -180,9 +176,11 @@ func (ki *keyIndex) isEmpty() bool {
 }
 
 // findGeneartion finds out the generation of the keyIndex that the
-// given index belongs to.
+// given rev belongs to. If the given rev is at the gap of two generations,
+// which means that the key does not exist at the given rev, it returns nil.
 func (ki *keyIndex) findGeneration(rev int64) *generation {
-	cg := len(ki.generations) - 1
+	lastg := len(ki.generations) - 1
+	cg := lastg
 
 	for cg >= 0 {
 		if len(ki.generations[cg].revs) == 0 {
@@ -190,6 +188,11 @@ func (ki *keyIndex) findGeneration(rev int64) *generation {
 			continue
 		}
 		g := ki.generations[cg]
+		if cg != lastg {
+			if tomb := g.revs[len(g.revs)-1].main; tomb <= rev {
+				return nil
+			}
+		}
 		if g.revs[0].main <= rev {
 			return &ki.generations[cg]
 		}
diff --git a/storage/key_index_test.go b/storage/key_index_test.go
index d419d9328..0490865ce 100644
--- a/storage/key_index_test.go
+++ b/storage/key_index_test.go
@@ -21,19 +21,19 @@ func TestKeyIndexGet(t *testing.T) {
 		wrev int64
 		werr error
 	}{
-		{13, 12, nil},
-		{13, 12, nil},
+		{13, 0, ErrRevisionNotFound},
+		{13, 0, ErrRevisionNotFound},
 
 		// get on generation 2
-		{12, 12, nil},
+		{12, 0, ErrRevisionNotFound},
 		{11, 10, nil},
 		{10, 10, nil},
 		{9, 8, nil},
 		{8, 8, nil},
-		{7, 6, nil},
+		{7, 0, ErrRevisionNotFound},
 
 		// get on generation 1
-		{6, 6, nil},
+		{6, 0, ErrRevisionNotFound},
 		{5, 4, nil},
 		{4, 4, nil},
 	}