diff --git a/tsdb/head_read.go b/tsdb/head_read.go
index 0ad885da20..45bbc81f18 100644
--- a/tsdb/head_read.go
+++ b/tsdb/head_read.go
@@ -582,10 +582,6 @@ func (s *memSeries) oooMergedChunks(meta chunks.Meta, cdm *chunks.ChunkDiskMappe
 	return mc, nil
 }
 
-func (o mergedOOOChunks) Iterator(iterator chunkenc.Iterator) chunkenc.Iterator {
-	return storage.ChainSampleIteratorFromIterables(iterator, o.chunkIterables)
-}
-
 var _ chunkenc.Iterable = &boundedIterable{}
 
 // boundedIterable is an implementation of chunkenc.Iterable that uses a
diff --git a/tsdb/ooo_head_read.go b/tsdb/ooo_head_read.go
index 4985ebb987..ed0b3fd227 100644
--- a/tsdb/ooo_head_read.go
+++ b/tsdb/ooo_head_read.go
@@ -49,6 +49,10 @@ type mergedOOOChunks struct {
 	chunkIterables []chunkenc.Iterable
 }
 
+func (o mergedOOOChunks) Iterator(iterator chunkenc.Iterator) chunkenc.Iterator {
+	return storage.ChainSampleIteratorFromIterables(iterator, o.chunkIterables)
+}
+
 func NewOOOHeadIndexReader(head *Head, mint, maxt int64, lastGarbageCollectedMmapRef chunks.ChunkDiskMapperRef) *OOOHeadIndexReader {
 	hr := &headIndexReader{
 		head: head,