diff --git a/storage/local/storage.go b/storage/local/storage.go
index 8f57617dd..d221097b3 100644
--- a/storage/local/storage.go
+++ b/storage/local/storage.go
@@ -946,6 +946,7 @@ func (s *MemorySeriesStorage) Append(sample *model.Sample) error {
 		s.discardedSamples.WithLabelValues(outOfOrderTimestamp).Inc()
 		return ErrOutOfOrderSample // Caused by the caller.
 	}
+	headChunkWasClosed := series.headChunkClosed
 	completedChunksCount, err := series.add(model.SamplePair{
 		Value:     sample.Value,
 		Timestamp: sample.Timestamp,
@@ -954,6 +955,11 @@ func (s *MemorySeriesStorage) Append(sample *model.Sample) error {
 		s.quarantineSeries(fp, sample.Metric, err)
 		return err
 	}
+	if headChunkWasClosed {
+		// Appending to a series with a closed head chunk creates an
+		// additional open head chunk.
+		s.headChunks.Inc()
+	}
 	s.ingestedSamples.Inc()
 	s.incNumChunksToPersist(completedChunksCount)