diff --git a/tsdb/engine/tsm1/reader.go b/tsdb/engine/tsm1/reader.go
index a3e5ddf3e7d..023292fec01 100644
--- a/tsdb/engine/tsm1/reader.go
+++ b/tsdb/engine/tsm1/reader.go
@@ -1309,7 +1309,7 @@ func (d *indirectIndex) Close() error {
 // blockaccessor abstracts a method of accessing blocks from a
 // TSM file through the accessor.
 type blockAccessor interface {
-	length() int
+	length() int64
 	read(int64, int64) []byte
 	free() error
 	advise(bool) error
@@ -1338,8 +1338,8 @@ func NewMMapAccessor(f *os.File) (*mmapAccessor, error) {
 	return t, nil
 }
 
-func (m *mmapAccessor) length() int {
-	return len(m.b)
+func (m *mmapAccessor) length() int64 {
+	return int64(len(m.b))
 }
 
 func (m *mmapAccessor) read(start int64, stop int64) []byte {
@@ -1360,7 +1360,7 @@ func (m *mmapAccessor) advise(need bool) error {
 
 type seekAccessor struct {
 	f *os.File
-	l int
+	l int64
 }
 
 func NewSeekAccessor(f *os.File) (*seekAccessor, error) {
@@ -1372,11 +1372,11 @@ func NewSeekAccessor(f *os.File) (*seekAccessor, error) {
 	}
 	t.f = f
 	// TSM files are immutable so their size won't change
-	t.l = int(stat.Size())
+	t.l = stat.Size()
 	return t, nil
 }
 
-func (m *seekAccessor) length() int {
+func (m *seekAccessor) length() int64 {
 	return m.l
 }
 
@@ -1403,8 +1403,8 @@ func (m *seekAccessor) advise(need bool) error {
 // Access is mmap based block accessor.  It access blocks through an
 // MMAP or seek/read file interface, depending on the type of blockAccessor
 type accessor struct {
-	accessCount uint64 // Counter incremented everytime the accessor is accessed
-	freeCount   uint64 // Counter to determine whether the accessor can free its resources
+	accessCount *uint64 // Counter incremented everytime the accessor is accessed
+	freeCount   *uint64 // Counter to determine whether the accessor can free its resources
 
 	mmapWillNeed bool // If true then mmap advise value MADV_WILLNEED will be provided the kernel for b.
 	useSeek bool // If true, use seekAccessor instead of mmapAccessor
@@ -1424,6 +1424,9 @@ func (m *accessor) init() (*indirectIndex, error) {
 		return nil, err
 	}
 
+	m.freeCount = new(uint64)
+	m.accessCount = new(uint64)
+
 	var err error
 	if (m.useSeek) {
 		m.b, err = NewSeekAccessor(m.f)
@@ -1461,14 +1464,14 @@ func (m *accessor) init() (*indirectIndex, error) {
 
 	// Allow resources to be freed immediately if requested
 	m.incAccess()
-	atomic.StoreUint64(&m.freeCount, 1)
+	atomic.StoreUint64(m.freeCount, 1)
 
 	return m.index, nil
 }
 
 func (m *accessor) free() error {
-	accessCount := atomic.LoadUint64(&m.accessCount)
-	freeCount := atomic.LoadUint64(&m.freeCount)
+	accessCount := atomic.LoadUint64(m.accessCount)
+	freeCount := atomic.LoadUint64(m.freeCount)
 
 	// Already freed everything.
 	if freeCount == 0 && accessCount == 0 {
@@ -1479,13 +1482,13 @@ func (m *accessor) free() error {
 	// If so, don't free anything and record the access count that we
 	// see now for the next check.
 	if accessCount != freeCount {
-		atomic.StoreUint64(&m.freeCount, accessCount)
+		atomic.StoreUint64(m.freeCount, accessCount)
 		return nil
 	}
 
 	// Reset both counters to zero to indicate that we have freed everything.
-	atomic.StoreUint64(&m.accessCount, 0)
-	atomic.StoreUint64(&m.freeCount, 0)
+	atomic.StoreUint64(m.accessCount, 0)
+	atomic.StoreUint64(m.freeCount, 0)
 
 	m.mu.RLock()
 	defer m.mu.RUnlock()
@@ -1494,7 +1497,7 @@ func (m *accessor) free() error {
 }
 
 func (m *accessor) incAccess() {
-	atomic.AddUint64(&m.accessCount, 1)
+	atomic.AddUint64(m.accessCount, 1)
 }
 
 func (m *accessor) rename(path string) error {