diff --git a/chunks/bstream.go b/chunks/bstream.go
index 6c3d4fee70..25fadb26d2 100644
--- a/chunks/bstream.go
+++ b/chunks/bstream.go
@@ -99,6 +99,10 @@ func (b *bstream) readBit() (bit, error) {
 	return d != 0, nil
 }
 
+func (b *bstream) ReadByte() (byte, error) {
+	return b.readByte()
+}
+
 func (b *bstream) readByte() (byte, error) {
 	if len(b.stream) == 0 {
 		return 0, io.EOF
diff --git a/chunks/chunk_test.go b/chunks/chunk_test.go
index 95829d66a3..c7cd8694e4 100644
--- a/chunks/chunk_test.go
+++ b/chunks/chunk_test.go
@@ -90,7 +90,8 @@ func benchmarkIterator(b *testing.B, newChunk func(int) Chunk) {
 	)
 	var exp []pair
 	for i := 0; i < b.N; i++ {
-		t += int64(rand.Intn(10000) + 1)
+		// t += int64(rand.Intn(10000) + 1)
+		t += int64(1000)
 		// v = rand.Float64()
 		v += float64(100)
 		exp = append(exp, pair{t: t, v: v})
@@ -156,7 +157,8 @@ func benchmarkAppender(b *testing.B, newChunk func(int) Chunk) {
 	)
 	var exp []pair
 	for i := 0; i < b.N; i++ {
-		t += int64(rand.Intn(10000) + 1)
+		// t += int64(rand.Intn(10000) + 1)
+		t += int64(1000)
 		// v = rand.Float64()
 		v += float64(100)
 		exp = append(exp, pair{t: t, v: v})
diff --git a/chunks/xor.go b/chunks/xor.go
index 8eda98aaec..2af1353d45 100644
--- a/chunks/xor.go
+++ b/chunks/xor.go
@@ -90,14 +90,20 @@ func (a *xorAppender) Append(t int64, v float64) error {
 	var tDelta uint64
 
 	if a.c.num == 0 {
-		// TODO: store varint time?
-		a.b.writeBits(uint64(t), 64)
+		buf := make([]byte, binary.MaxVarintLen64)
+		for _, b := range buf[:binary.PutVarint(buf, t)] {
+			a.b.writeByte(b)
+		}
 		a.b.writeBits(math.Float64bits(v), 64)
 
 	} else if a.c.num == 1 {
 		tDelta = uint64(t - a.t)
-		// TODO: use varint or other encoding for first delta?
-		a.b.writeBits(tDelta, 64)
+
+		buf := make([]byte, binary.MaxVarintLen64)
+		for _, b := range buf[:binary.PutUvarint(buf, tDelta)] {
+			a.b.writeByte(b)
+		}
+
 		a.writeVDelta(v)
 
 	} else {
@@ -203,7 +209,7 @@ func (it *xorIterator) Next() bool {
 	}
 
 	if it.numRead == 0 {
-		t, err := it.br.readBits(64)
+		t, err := binary.ReadVarint(it.br)
 		if err != nil {
 			it.err = err
 			return false
@@ -220,7 +226,7 @@ func (it *xorIterator) Next() bool {
 		return true
 	}
 	if it.numRead == 1 {
-		tDelta, err := it.br.readBits(64)
+		tDelta, err := binary.ReadUvarint(it.br)
 		if err != nil {
 			it.err = err
 			return false