diff --git a/db.go b/db.go
index f4902f4d5e..2d7e215012 100644
--- a/db.go
+++ b/db.go
@@ -226,6 +226,9 @@ func OpenShard(path string, logger log.Logger) (*Shard, error) {
 
 // Close the shard.
 func (s *Shard) Close() error {
+	s.mtx.Lock()
+	defer s.mtx.Unlock()
+
 	var e MultiError
 
 	for _, pb := range s.persisted {
diff --git a/querier.go b/querier.go
index d4c8945b31..3f3f1e213f 100644
--- a/querier.go
+++ b/querier.go
@@ -120,23 +120,33 @@ func (q *querier) LabelValuesFor(string, labels.Label) ([]string, error) {
 }
 
 func (q *querier) Close() error {
-	return nil
+	var merr MultiError
+
+	for _, sq := range q.shards {
+		merr.Add(sq.Close())
+	}
+	return merr.Err()
 }
 
 // shardQuerier aggregates querying results from time blocks within
 // a single shard.
 type shardQuerier struct {
+	shard  *Shard
 	blocks []Querier
 }
 
 // Querier returns a new querier over the data shard for the given
 // time range.
 func (s *Shard) Querier(mint, maxt int64) Querier {
+	s.mtx.RLock()
+
 	blocks := s.blocksForInterval(mint, maxt)
 
 	sq := &shardQuerier{
 		blocks: make([]Querier, 0, len(blocks)),
+		shard:  s,
 	}
+
 	for _, b := range blocks {
 		sq.blocks = append(sq.blocks, b.Querier(mint, maxt))
 	}
@@ -182,7 +192,14 @@ func (q *shardQuerier) Select(ms ...labels.Matcher) SeriesSet {
 }
 
 func (q *shardQuerier) Close() error {
-	return nil
+	var merr MultiError
+
+	for _, bq := range q.blocks {
+		merr.Add(bq.Close())
+	}
+	q.shard.mtx.RUnlock()
+
+	return merr.Err()
 }
 
 // blockQuerier provides querying access to a single block database.