diff --git a/block.go b/block.go
index dd6a6def8..19425ba4c 100644
--- a/block.go
+++ b/block.go
@@ -474,7 +474,7 @@ func (pb *Block) CleanTombstones(dest string, c Compactor) (bool, error) {
 	numStones := 0
 
 	pb.tombstones.Iter(func(id uint64, ivs Intervals) error {
-		for _ = range ivs {
+		for range ivs {
 			numStones++
 		}
 
diff --git a/chunkenc/xor.go b/chunkenc/xor.go
index ff690f222..0f14cf720 100644
--- a/chunkenc/xor.go
+++ b/chunkenc/xor.go
@@ -259,7 +259,7 @@ func (it *xorIterator) Next() bool {
 			it.err = err
 			return false
 		}
-		it.t = int64(t)
+		it.t = t
 		it.val = math.Float64frombits(v)
 
 		it.numRead++
diff --git a/chunks/chunks.go b/chunks/chunks.go
index e32ea0f99..9c80767ff 100644
--- a/chunks/chunks.go
+++ b/chunks/chunks.go
@@ -133,7 +133,7 @@ func (w *Writer) finalizeTail() error {
 		return err
 	}
 	// As the file was pre-allocated, we truncate any superfluous zero bytes.
-	off, err := tf.Seek(0, os.SEEK_CUR)
+	off, err := tf.Seek(0, io.SeekCurrent)
 	if err != nil {
 		return err
 	}
@@ -349,7 +349,7 @@ func (s *Reader) Chunk(ref uint64) (chunkenc.Chunk, error) {
 	}
 	b := s.bs[seq]
 
-	if int(off) >= b.Len() {
+	if off >= b.Len() {
 		return nil, errors.Errorf("offset %d beyond data size %d", off, b.Len())
 	}
 	// With the minimum chunk length this should never cause us reading
diff --git a/db.go b/db.go
index 489f3a12e..53bc65ade 100644
--- a/db.go
+++ b/db.go
@@ -725,10 +725,7 @@ func (db *DB) Delete(mint, maxt int64, ms ...labels.Matcher) error {
 	g.Go(func() error {
 		return db.head.Delete(mint, maxt, ms...)
 	})
-	if err := g.Wait(); err != nil {
-		return err
-	}
-	return nil
+	return g.Wait()
 }
 
 // CleanTombstones re-writes any blocks with tombstones.
@@ -737,7 +734,7 @@ func (db *DB) CleanTombstones() error {
 	defer db.cmtx.Unlock()
 
 	start := time.Now()
-	defer db.metrics.tombCleanTimer.Observe(float64(time.Since(start).Seconds()))
+	defer db.metrics.tombCleanTimer.Observe(time.Since(start).Seconds())
 
 	db.mtx.RLock()
 	blocks := db.blocks[:]
diff --git a/index/index.go b/index/index.go
index 3cad716c0..72ca3835a 100644
--- a/index/index.go
+++ b/index/index.go
@@ -780,7 +780,7 @@ func (r *Reader) readSymbols(off int) error {
 
 	for d.err() == nil && d.len() > 0 && cnt > 0 {
 		s := d.uvarintStr()
-		r.symbols[uint32(nextPos)] = s
+		r.symbols[nextPos] = s
 
 		if r.version == 2 {
 			nextPos++
@@ -800,7 +800,7 @@ func (r *Reader) readOffsetTable(off uint64, f func([]string, uint64) error) err
 	cnt := d.be32()
 
 	for d.err() == nil && d.len() > 0 && cnt > 0 {
-		keyCount := int(d.uvarint())
+		keyCount := d.uvarint()
 		keys := make([]string, 0, keyCount)
 
 		for i := 0; i < keyCount; i++ {
@@ -1038,7 +1038,7 @@ func (dec *Decoder) Series(b []byte, lbls *labels.Labels, chks *[]chunks.Meta) e
 
 	d := decbuf{b: b}
 
-	k := int(d.uvarint())
+	k := d.uvarint()
 
 	for i := 0; i < k; i++ {
 		lno := uint32(d.uvarint())
@@ -1061,7 +1061,7 @@ func (dec *Decoder) Series(b []byte, lbls *labels.Labels, chks *[]chunks.Meta) e
 	}
 
 	// Read the chunks meta data.
-	k = int(d.uvarint())
+	k = d.uvarint()
 
 	if k == 0 {
 		return nil
diff --git a/wal.go b/wal.go
index 72e8bc070..3f1cf7d45 100644
--- a/wal.go
+++ b/wal.go
@@ -290,7 +290,7 @@ func (w *SegmentWAL) truncate(err error, file int, lastOffset int64) error {
 	w.files = w.files[:file+1]
 
 	// Seek the current file to the last valid offset where we continue writing from.
-	_, err = w.files[file].Seek(lastOffset, os.SEEK_SET)
+	_, err = w.files[file].Seek(lastOffset, io.SeekStart)
 	return err
 }
 
@@ -393,7 +393,7 @@ func (w *SegmentWAL) Truncate(mint int64, keep func(uint64) bool) error {
 		return errors.Wrap(r.Err(), "read candidate WAL files")
 	}
 
-	off, err := csf.Seek(0, os.SEEK_CUR)
+	off, err := csf.Seek(0, io.SeekCurrent)
 	if err != nil {
 		return err
 	}
@@ -583,7 +583,7 @@ func (w *SegmentWAL) cut() error {
 		// in the new segment.
 		go func() {
 			w.actorc <- func() error {
-				off, err := hf.Seek(0, os.SEEK_CUR)
+				off, err := hf.Seek(0, io.SeekCurrent)
 				if err != nil {
 					return errors.Wrapf(err, "finish old segment %s", hf.Name())
 				}
@@ -1024,7 +1024,7 @@ func (r *walReader) next() bool {
 
 	// Remember the offset after the last correctly read entry. If the next one
 	// is corrupted, this is where we can safely truncate.
-	r.lastOffset, r.err = cf.Seek(0, os.SEEK_CUR)
+	r.lastOffset, r.err = cf.Seek(0, io.SeekCurrent)
 	if r.err != nil {
 		return false
 	}
diff --git a/wal_test.go b/wal_test.go
index c6552eb62..6d559f5d9 100644
--- a/wal_test.go
+++ b/wal_test.go
@@ -15,6 +15,7 @@ package tsdb
 
 import (
 	"encoding/binary"
+	"io"
 	"io/ioutil"
 	"math/rand"
 	"os"
@@ -305,7 +306,7 @@ func TestWALRestoreCorrupted(t *testing.T) {
 				testutil.Ok(t, err)
 				defer f.Close()
 
-				off, err := f.Seek(0, os.SEEK_END)
+				off, err := f.Seek(0, io.SeekEnd)
 				testutil.Ok(t, err)
 
 				testutil.Ok(t, f.Truncate(off-1))
@@ -318,7 +319,7 @@ func TestWALRestoreCorrupted(t *testing.T) {
 				testutil.Ok(t, err)
 				defer f.Close()
 
-				off, err := f.Seek(0, os.SEEK_END)
+				off, err := f.Seek(0, io.SeekEnd)
 				testutil.Ok(t, err)
 
 				testutil.Ok(t, f.Truncate(off-8))
@@ -331,7 +332,7 @@ func TestWALRestoreCorrupted(t *testing.T) {
 				testutil.Ok(t, err)
 				defer f.Close()
 
-				off, err := f.Seek(0, os.SEEK_END)
+				off, err := f.Seek(0, io.SeekEnd)
 				testutil.Ok(t, err)
 
 				// Write junk before checksum starts.
@@ -346,7 +347,7 @@ func TestWALRestoreCorrupted(t *testing.T) {
 				testutil.Ok(t, err)
 				defer f.Close()
 
-				off, err := f.Seek(0, os.SEEK_END)
+				off, err := f.Seek(0, io.SeekEnd)
 				testutil.Ok(t, err)
 
 				// Write junk into checksum