diff --git a/tsdb/engine.go b/tsdb/engine.go
index 87e9408ab2..fc781fbfe7 100644
--- a/tsdb/engine.go
+++ b/tsdb/engine.go
@@ -45,7 +45,7 @@ type Engine interface {
 	Export(w io.Writer, basePath string, start time.Time, end time.Time) error
 	Restore(r io.Reader, basePath string) error
 	Import(r io.Reader, basePath string) error
-	Digest() (io.ReadCloser, error)
+	Digest() (io.ReadCloser, int64, error)
 
 	CreateIterator(ctx context.Context, measurement string, opt query.IteratorOptions) (query.Iterator, error)
 	CreateCursor(ctx context.Context, r *CursorRequest) (Cursor, error)
diff --git a/tsdb/engine/tsm1/engine.go b/tsdb/engine/tsm1/engine.go
index 96efbd339a..3623997cc8 100644
--- a/tsdb/engine/tsm1/engine.go
+++ b/tsdb/engine/tsm1/engine.go
@@ -229,7 +229,7 @@ func NewEngine(id uint64, idx tsdb.Index, database, path string, walPath string,
 }
 
 // Digest returns a reader for the shard's digest.
-func (e *Engine) Digest() (io.ReadCloser, error) {
+func (e *Engine) Digest() (io.ReadCloser, int64, error) {
 	digestPath := filepath.Join(e.path, "digest.tsd")
 
 	// See if there's an existing digest file on disk.
@@ -239,16 +239,21 @@ func (e *Engine) Digest() (io.ReadCloser, error) {
 		fi, err := f.Stat()
 		if err != nil {
 			f.Close()
-			return nil, err
+			return nil, 0, err
 		}
 
 		if !e.LastModified().After(fi.ModTime()) {
 			// Existing digest is still fresh so return a reader for it.
-			return f, nil
+			fi, err := f.Stat()
+			if err != nil {
+				f.Close()
+				return nil, 0, err
+			}
+			return f, fi.Size(), nil
 		}
 
 		if err := f.Close(); err != nil {
-			return nil, err
+			return nil, 0, err
 		}
 	}
 
@@ -258,23 +263,34 @@ func (e *Engine) Digest() (io.ReadCloser, error) {
 	// Create a tmp file to write the digest to.
 	tf, err := os.Create(digestPath + ".tmp")
 	if err != nil {
-		return nil, err
+		return nil, 0, err
 	}
 
 	// Write the new digest to the tmp file.
 	if err := Digest(e.path, tf); err != nil {
 		tf.Close()
 		os.Remove(tf.Name())
-		return nil, err
+		return nil, 0, err
 	}
 
 	// Rename the temporary digest file to the actual digest file.
 	if err := renameFile(tf.Name(), digestPath); err != nil {
-		return nil, err
+		return nil, 0, err
 	}
 
 	// Create and return a reader for the new digest file.
-	return os.Open(digestPath)
+	f, err = os.Open(digestPath)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	fi, err := f.Stat()
+	if err != nil {
+		f.Close()
+		return nil, 0, err
+	}
+
+	return f, fi.Size(), nil
 }
 
 // SetEnabled sets whether the engine is enabled.
diff --git a/tsdb/engine/tsm1/engine_test.go b/tsdb/engine/tsm1/engine_test.go
index 74f9284e37..c5efeb57e8 100644
--- a/tsdb/engine/tsm1/engine_test.go
+++ b/tsdb/engine/tsm1/engine_test.go
@@ -90,11 +90,15 @@ func TestEngine_Digest(t *testing.T) {
 
 	digest := func() ([]span, error) {
 		// Get a reader for the shard's digest.
-		r, err := e.Digest()
+		r, sz, err := e.Digest()
 		if err != nil {
 			return nil, err
 		}
 
+		if sz <= 0 {
+			t.Fatalf("expected digest size > 0")
+		}
+
 		// Make sure the digest can be read.
 		dr, err := tsm1.NewDigestReader(r)
 		if err != nil {
diff --git a/tsdb/shard.go b/tsdb/shard.go
index efebef4295..3ac5a096e1 100644
--- a/tsdb/shard.go
+++ b/tsdb/shard.go
@@ -1112,16 +1112,16 @@ func (s *Shard) TagKeyCardinality(name, key []byte) int {
 }
 
 // Digest returns a digest of the shard.
-func (s *Shard) Digest() (io.ReadCloser, error) {
+func (s *Shard) Digest() (io.ReadCloser, int64, error) {
 	engine, err := s.engine()
 	if err != nil {
-		return nil, err
+		return nil, 0, err
 	}
 
 	// Make sure the shard is idle/cold. (No use creating a digest of a
 	// hot shard that is rapidly changing.)
 	if !engine.IsIdle() {
-		return nil, ErrShardNotIdle
+		return nil, 0, ErrShardNotIdle
 	}
 
 	return engine.Digest()
diff --git a/tsdb/store.go b/tsdb/store.go
index 31447692f5..22e0dbf620 100644
--- a/tsdb/store.go
+++ b/tsdb/store.go
@@ -439,10 +439,10 @@ func (s *Store) ShardN() int {
 }
 
 // ShardDigest returns a digest of the shard with the specified ID.
-func (s *Store) ShardDigest(id uint64) (io.ReadCloser, error) {
+func (s *Store) ShardDigest(id uint64) (io.ReadCloser, int64, error) {
 	sh := s.Shard(id)
 	if sh == nil {
-		return nil, ErrShardNotFound
+		return nil, 0, ErrShardNotFound
 	}
 
 	return sh.Digest()