diff --git a/tsdb/head.go b/tsdb/head.go
index 213846aa35..8db9231124 100644
--- a/tsdb/head.go
+++ b/tsdb/head.go
@@ -2101,20 +2101,20 @@ func (s *stripeSeries) postCreation(lset labels.Labels) {
 }
 
 type sample struct {
+	st int64
 	t  int64
 	f  float64
 	h  *histogram.Histogram
 	fh *histogram.FloatHistogram
 }
 
-func newSample(t int64, v float64, h *histogram.Histogram, fh *histogram.FloatHistogram) chunks.Sample {
-	return sample{t, v, h, fh}
+func newSample(st, t int64, v float64, h *histogram.Histogram, fh *histogram.FloatHistogram) chunks.Sample {
+	return sample{st, t, v, h, fh}
 }
 
 func (s sample) T() int64 { return s.t }
 
-// TODO(krajorama): implement ST.
-func (sample) ST() int64                       { return 0 }
+func (s sample) ST() int64                     { return s.st }
 func (s sample) F() float64                    { return s.f }
 func (s sample) H() *histogram.Histogram       { return s.h }
 func (s sample) FH() *histogram.FloatHistogram { return s.fh }