diff --git a/block.go b/block.go
index 42e11d951..3ed8c4a64 100644
--- a/block.go
+++ b/block.go
@@ -282,7 +282,7 @@ func OpenBlock(logger log.Logger, dir string, pool chunkenc.Pool) (*Block, error
 	if err != nil {
 		return nil, err
 	}
-	ir, err := index.NewFileReader(filepath.Join(dir, "index"))
+	ir, err := index.NewFileReader(filepath.Join(dir, indexFilename))
 	if err != nil {
 		return nil, err
 	}
diff --git a/index/index.go b/index/index.go
index 74e08d465..ca33eac3f 100644
--- a/index/index.go
+++ b/index/index.go
@@ -45,6 +45,8 @@ const (
 	FormatV2 = 2
 
 	labelNameSeperator = "\xff"
+
+	indexFilename = "index"
 )
 
 type indexWriterSeries struct {
diff --git a/index/index_test.go b/index/index_test.go
index 2edd3956a..25c5be938 100644
--- a/index/index_test.go
+++ b/index/index_test.go
@@ -151,7 +151,7 @@ func TestIndexRW_Create_Open(t *testing.T) {
 	testutil.Ok(t, err)
 	defer os.RemoveAll(dir)
 
-	fn := filepath.Join(dir, "index")
+	fn := filepath.Join(dir, indexFilename)
 
 	// An empty index must still result in a readable file.
 	iw, err := NewWriter(fn)
@@ -177,7 +177,7 @@ func TestIndexRW_Postings(t *testing.T) {
 	testutil.Ok(t, err)
 	defer os.RemoveAll(dir)
 
-	fn := filepath.Join(dir, "index")
+	fn := filepath.Join(dir, indexFilename)
 
 	iw, err := NewWriter(fn)
 	testutil.Ok(t, err)
@@ -271,7 +271,7 @@ func TestPersistence_index_e2e(t *testing.T) {
 		})
 	}
 
-	iw, err := NewWriter(filepath.Join(dir, "index"))
+	iw, err := NewWriter(filepath.Join(dir, indexFilename))
 	testutil.Ok(t, err)
 
 	testutil.Ok(t, iw.AddSymbols(symbols))
@@ -331,7 +331,7 @@ func TestPersistence_index_e2e(t *testing.T) {
 	err = iw.Close()
 	testutil.Ok(t, err)
 
-	ir, err := NewFileReader(filepath.Join(dir, "index"))
+	ir, err := NewFileReader(filepath.Join(dir, indexFilename))
 	testutil.Ok(t, err)
 
 	for p := range mi.postings {
diff --git a/repair.go b/repair.go
index 15f79d5f7..4aeffb554 100644
--- a/repair.go
+++ b/repair.go
@@ -64,7 +64,7 @@ func repairBadIndexVersion(logger log.Logger, dir string) error {
 		if err != nil {
 			return wrapErr(err, d)
 		}
-		broken, err := os.Open(filepath.Join(d, "index"))
+		broken, err := os.Open(filepath.Join(d, indexFilename))
 		if err != nil {
 			return wrapErr(err, d)
 		}
diff --git a/repair_test.go b/repair_test.go
index 5fb780a5b..cbe21691e 100644
--- a/repair_test.go
+++ b/repair_test.go
@@ -30,7 +30,7 @@ func TestRepairBadIndexVersion(t *testing.T) {
 	// at a broken revision.
 	//
 	// func main() {
-	// 	w, err := index.NewWriter("index")
+	// 	w, err := index.NewWriter(indexFilename)
 	// 	if err != nil {
 	// 		panic(err)
 	// 	}
@@ -72,7 +72,7 @@ func TestRepairBadIndexVersion(t *testing.T) {
 	os.MkdirAll(filepath.Join(dbDir, "chunks"), 0777)
 	defer os.RemoveAll(filepath.Join(dbDir, "chunks"))
 
-	r, err := index.NewFileReader(filepath.Join(dbDir, "index"))
+	r, err := index.NewFileReader(filepath.Join(dbDir, indexFilename))
 	testutil.Ok(t, err)
 	p, err := r.Postings("b", "1")
 	testutil.Ok(t, err)
@@ -95,7 +95,7 @@ func TestRepairBadIndexVersion(t *testing.T) {
 	testutil.Ok(t, err)
 	db.Close()
 
-	r, err = index.NewFileReader(filepath.Join(tmpDbDir, "index"))
+	r, err = index.NewFileReader(filepath.Join(tmpDbDir, indexFilename))
 	testutil.Ok(t, err)
 	p, err = r.Postings("b", "1")
 	testutil.Ok(t, err)