diff --git a/block.go b/block.go
index 664ead49e..1a45fb971 100644
--- a/block.go
+++ b/block.go
@@ -434,7 +434,7 @@ func (pb *Block) Delete(mint, maxt int64, ms ...labels.Matcher) error {
 	ir := pb.indexr
 
 	// Choose only valid postings which have chunks in the time-range.
-	stones := memTombstones{}
+	stones := NewMemTombstones()
 
 	var lset labels.Labels
 	var chks []chunks.Meta
@@ -450,7 +450,7 @@ Outer:
 			if chk.OverlapsClosedInterval(mint, maxt) {
 				// Delete only until the current values and not beyond.
 				tmin, tmax := clampInterval(mint, maxt, chks[0].MinTime, chks[len(chks)-1].MaxTime)
-				stones[p.At()] = Intervals{{tmin, tmax}}
+				stones.addInterval(p.At(), Interval{tmin, tmax})
 				continue Outer
 			}
 		}
@@ -462,7 +462,7 @@ Outer:
 
 	err = pb.tombstones.Iter(func(id uint64, ivs Intervals) error {
 		for _, iv := range ivs {
-			stones.add(id, iv)
+			stones.addInterval(id, iv)
 			pb.meta.Stats.NumTombstones++
 		}
 		return nil
diff --git a/block_test.go b/block_test.go
index 5d02a1617..93f145e64 100644
--- a/block_test.go
+++ b/block_test.go
@@ -67,7 +67,7 @@ func createEmptyBlock(t *testing.T, dir string, meta *BlockMeta) *Block {
 
 	testutil.Ok(t, os.MkdirAll(chunkDir(dir), 0777))
 
-	testutil.Ok(t, writeTombstoneFile(dir, EmptyTombstoneReader()))
+	testutil.Ok(t, writeTombstoneFile(dir, NewMemTombstones()))
 
 	b, err := OpenBlock(dir, nil)
 	testutil.Ok(t, err)
diff --git a/compact.go b/compact.go
index aae8cc1c2..1da130057 100644
--- a/compact.go
+++ b/compact.go
@@ -483,7 +483,7 @@ func (c *LeveledCompactor) write(dest string, meta *BlockMeta, blocks ...BlockRe
 	}
 
 	// Create an empty tombstones file.
-	if err := writeTombstoneFile(tmp, EmptyTombstoneReader()); err != nil {
+	if err := writeTombstoneFile(tmp, NewMemTombstones()); err != nil {
 		return errors.Wrap(err, "write new tombstones file")
 	}
 
diff --git a/db_test.go b/db_test.go
index 7ed21aaca..205b0f844 100644
--- a/db_test.go
+++ b/db_test.go
@@ -780,7 +780,7 @@ func TestTombstoneClean(t *testing.T) {
 		}
 
 		for _, b := range db.blocks {
-			testutil.Equals(t, emptyTombstoneReader, b.tombstones)
+			testutil.Equals(t, NewMemTombstones(), b.tombstones)
 		}
 	}
 }
@@ -809,8 +809,8 @@ func TestTombstoneCleanFail(t *testing.T) {
 		block := createEmptyBlock(t, blockDir, meta)
 
 		// Add some some fake tombstones to trigger the compaction.
-		tomb := memTombstones{}
-		tomb[0] = Intervals{{0, 1}}
+		tomb := NewMemTombstones()
+		tomb.addInterval(0, Interval{0, 1})
 		block.tombstones = tomb
 
 		db.blocks = append(db.blocks, block)
diff --git a/head.go b/head.go
index c694d20ca..372842865 100644
--- a/head.go
+++ b/head.go
@@ -69,7 +69,7 @@ type Head struct {
 
 	postings *index.MemPostings // postings lists for terms
 
-	tombstones memTombstones
+	tombstones *memTombstones
 }
 
 type headMetrics struct {
@@ -189,7 +189,7 @@ func NewHead(r prometheus.Registerer, l log.Logger, wal WAL, chunkRange int64) (
 		values:     map[string]stringset{},
 		symbols:    map[string]struct{}{},
 		postings:   index.NewUnorderedMemPostings(),
-		tombstones: memTombstones{},
+		tombstones: NewMemTombstones(),
 	}
 	h.metrics = newHeadMetrics(h, r)
 
@@ -300,7 +300,7 @@ func (h *Head) ReadWAL() error {
 				if itv.Maxt < mint {
 					continue
 				}
-				h.tombstones.add(s.ref, itv)
+				h.tombstones.addInterval(s.ref, itv)
 			}
 		}
 	}
@@ -605,7 +605,7 @@ func (h *Head) Delete(mint, maxt int64, ms ...labels.Matcher) error {
 		return err
 	}
 	for _, s := range stones {
-		h.tombstones.add(s.ref, s.intervals[0])
+		h.tombstones.addInterval(s.ref, s.intervals[0])
 	}
 	return nil
 }
diff --git a/head_test.go b/head_test.go
index 2944bb672..9a8c89364 100644
--- a/head_test.go
+++ b/head_test.go
@@ -315,7 +315,7 @@ func TestHeadDeleteSimple(t *testing.T) {
 Outer:
 	for _, c := range cases {
 		// Reset the tombstones.
-		head.tombstones = memTombstones{}
+		head.tombstones = NewMemTombstones()
 
 		// Delete the ranges.
 		for _, r := range c.intervals {
diff --git a/querier.go b/querier.go
index b5b9ae050..2e048e495 100644
--- a/querier.go
+++ b/querier.go
@@ -478,7 +478,7 @@ type baseChunkSeries struct {
 // over them. It drops chunks based on tombstones in the given reader.
 func LookupChunkSeries(ir IndexReader, tr TombstoneReader, ms ...labels.Matcher) (ChunkSeriesSet, error) {
 	if tr == nil {
-		tr = EmptyTombstoneReader()
+		tr = NewMemTombstones()
 	}
 	p, err := PostingsForMatchers(ir, ms...)
 	if err != nil {
diff --git a/querier_test.go b/querier_test.go
index 2eb10471c..fd8c7dec5 100644
--- a/querier_test.go
+++ b/querier_test.go
@@ -457,7 +457,7 @@ Outer:
 		querier := &blockQuerier{
 			index:      ir,
 			chunks:     cr,
-			tombstones: EmptyTombstoneReader(),
+			tombstones: NewMemTombstones(),
 
 			mint: c.mint,
 			maxt: c.maxt,
@@ -557,12 +557,11 @@ func TestBlockQuerierDelete(t *testing.T) {
 				},
 			},
 		},
-		tombstones: memTombstones{
+		tombstones: &memTombstones{intvlGroups: map[uint64]Intervals{
 			1: Intervals{{1, 3}},
 			2: Intervals{{1, 3}, {6, 10}},
 			3: Intervals{{6, 10}},
-		},
-
+		}},
 		queries: []query{
 			{
 				mint: 2,
@@ -737,7 +736,7 @@ func TestBaseChunkSeries(t *testing.T) {
 		bcs := &baseChunkSeries{
 			p:          index.NewListPostings(tc.postings),
 			index:      mi,
-			tombstones: EmptyTombstoneReader(),
+			tombstones: NewMemTombstones(),
 		}
 
 		i := 0
diff --git a/tombstones.go b/tombstones.go
index 8c760cdce..d4a3d0ef1 100644
--- a/tombstones.go
+++ b/tombstones.go
@@ -16,12 +16,12 @@ package tsdb
 import (
 	"encoding/binary"
 	"fmt"
+	"github.com/pkg/errors"
 	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
-
-	"github.com/pkg/errors"
+	"sync"
 )
 
 const tombstoneFilename = "tombstones"
@@ -107,10 +107,10 @@ type Stone struct {
 	intervals Intervals
 }
 
-func readTombstones(dir string) (memTombstones, error) {
+func readTombstones(dir string) (*memTombstones, error) {
 	b, err := ioutil.ReadFile(filepath.Join(dir, tombstoneFilename))
 	if os.IsNotExist(err) {
-		return memTombstones{}, nil
+		return NewMemTombstones(), nil
 	} else if err != nil {
 		return nil, err
 	}
@@ -140,7 +140,7 @@ func readTombstones(dir string) (memTombstones, error) {
 		return nil, errors.New("checksum did not match")
 	}
 
-	stonesMap := memTombstones{}
+	stonesMap := NewMemTombstones()
 
 	for d.len() > 0 {
 		k := d.uvarint64()
@@ -150,27 +150,31 @@ func readTombstones(dir string) (memTombstones, error) {
 			return nil, d.err()
 		}
 
-		stonesMap.add(k, Interval{mint, maxt})
+		stonesMap.addInterval(k, Interval{mint, maxt})
 	}
 
 	return stonesMap, nil
 }
 
-type memTombstones map[uint64]Intervals
-
-var emptyTombstoneReader = memTombstones{}
-
-// EmptyTombstoneReader returns a TombstoneReader that is always empty.
-func EmptyTombstoneReader() TombstoneReader {
-	return emptyTombstoneReader
+type memTombstones struct {
+	intvlGroups map[uint64]Intervals
+	mtx         sync.RWMutex
 }
 
-func (t memTombstones) Get(ref uint64) (Intervals, error) {
-	return t[ref], nil
+func NewMemTombstones() *memTombstones {
+	return &memTombstones{intvlGroups: make(map[uint64]Intervals)}
 }
 
-func (t memTombstones) Iter(f func(uint64, Intervals) error) error {
-	for ref, ivs := range t {
+func (t *memTombstones) Get(ref uint64) (Intervals, error) {
+	t.mtx.RLock()
+	defer t.mtx.RUnlock()
+	return t.intvlGroups[ref], nil
+}
+
+func (t *memTombstones) Iter(f func(uint64, Intervals) error) error {
+	t.mtx.RLock()
+	defer t.mtx.RUnlock()
+	for ref, ivs := range t.intvlGroups {
 		if err := f(ref, ivs); err != nil {
 			return err
 		}
@@ -178,8 +182,13 @@ func (t memTombstones) Iter(f func(uint64, Intervals) error) error {
 	return nil
 }
 
-func (t memTombstones) add(ref uint64, itv Interval) {
-	t[ref] = t[ref].add(itv)
+// addInterval to an existing memTombstones
+func (t *memTombstones) addInterval(ref uint64, itvs ...Interval) {
+	t.mtx.Lock()
+	defer t.mtx.Unlock()
+	for _, itv := range itvs {
+		t.intvlGroups[ref] = t.intvlGroups[ref].add(itv)
+	}
 }
 
 func (memTombstones) Close() error {
@@ -208,7 +217,7 @@ func (tr Interval) isSubrange(dranges Intervals) bool {
 // Intervals represents	a set of increasing and non-overlapping time-intervals.
 type Intervals []Interval
 
-// This adds the new time-range to the existing ones.
+// add the new time-range to the existing ones.
 // The existing ones must be sorted.
 func (itvs Intervals) add(n Interval) Intervals {
 	for i, r := range itvs {
diff --git a/tombstones_test.go b/tombstones_test.go
index c5c15ae17..62bc06818 100644
--- a/tombstones_test.go
+++ b/tombstones_test.go
@@ -17,6 +17,7 @@ import (
 	"io/ioutil"
 	"math/rand"
 	"os"
+	"sync"
 	"testing"
 	"time"
 
@@ -29,7 +30,7 @@ func TestWriteAndReadbackTombStones(t *testing.T) {
 
 	ref := uint64(0)
 
-	stones := memTombstones{}
+	stones := NewMemTombstones()
 	// Generate the tombstones.
 	for i := 0; i < 100; i++ {
 		ref += uint64(rand.Int31n(10)) + 1
@@ -40,7 +41,7 @@ func TestWriteAndReadbackTombStones(t *testing.T) {
 			dranges = dranges.add(Interval{mint, mint + rand.Int63n(1000)})
 			mint += rand.Int63n(1000) + 1
 		}
-		stones[ref] = dranges
+		stones.addInterval(ref, dranges...)
 	}
 
 	testutil.Ok(t, writeTombstoneFile(tmpdir, stones))
@@ -121,3 +122,25 @@ func TestAddingNewIntervals(t *testing.T) {
 	}
 	return
 }
+
+// TestMemTombstonesConcurrency to make sure they are safe to access from different goroutines.
+func TestMemTombstonesConcurrency(t *testing.T) {
+	tomb := NewMemTombstones()
+	totalRuns := 100
+	var wg sync.WaitGroup
+	wg.Add(2)
+
+	go func() {
+		for x := 0; x < totalRuns; x++ {
+			tomb.addInterval(uint64(x), Interval{int64(x), int64(x)})
+		}
+		wg.Done()
+	}()
+	go func() {
+		for x := 0; x < totalRuns; x++ {
+			tomb.Get(uint64(x))
+		}
+		wg.Done()
+	}()
+	wg.Wait()
+}