diff --git a/tests/server_helpers.go b/tests/server_helpers.go
index 223c74f8d6..90891fb122 100644
--- a/tests/server_helpers.go
+++ b/tests/server_helpers.go
@@ -338,6 +338,11 @@ func (s *LocalServer) Reset() error {
 func (s *LocalServer) WritePoints(database, retentionPolicy string, consistencyLevel models.ConsistencyLevel, user meta.User, points []models.Point) error {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
+
+	if s.PointsWriter == nil {
+		return fmt.Errorf("server closed")
+	}
+
 	return s.PointsWriter.WritePoints(database, retentionPolicy, consistencyLevel, user, points)
 }
 
diff --git a/tsdb/engine/tsm1/engine.go b/tsdb/engine/tsm1/engine.go
index 12ba3e061a..7b382a6774 100644
--- a/tsdb/engine/tsm1/engine.go
+++ b/tsdb/engine/tsm1/engine.go
@@ -1184,6 +1184,9 @@ func (e *Engine) deleteSeriesRange(seriesKeys [][]byte, min, max int64) error {
 		return nil
 	})
 
+	// Sort the series keys because ApplyEntryFn iterates over the keys randomly.
+	bytesutil.Sort(deleteKeys)
+
 	e.Cache.DeleteRange(deleteKeys, min, max)
 
 	// delete from the WAL