diff --git a/CHANGELOG.md b/CHANGELOG.md
index 623fa8f73..aec464e7f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,3 @@
-## 2.18.2 / 2020-06-09
-
-* [BUGFIX] TSDB: Fix incorrect query results when using Prometheus with remote reads configured #7361
-
 ## 2.18.1 / 2020-05-07
 
 * [BUGFIX] TSDB: Fixed snapshot API. #7217
diff --git a/VERSION b/VERSION
index 61dc3342f..a36e9b090 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.18.2
+2.18.1
diff --git a/storage/fanout_test.go b/storage/fanout_test.go
index a5d04ea8f..cc839b6ed 100644
--- a/storage/fanout_test.go
+++ b/storage/fanout_test.go
@@ -195,18 +195,10 @@ func TestMergeQuerierWithChainMerger(t *testing.T) {
 			}
 			qs = append(qs, tc.extraQueriers...)
 
-			mergedQuerier, _, _ := NewMergeQuerier(qs[0], qs, ChainedSeriesMerge).Select(false, nil)
-
-			// Get all merged series upfront to make sure there are no incorrectly retained shared
-			// buffers causing bugs.
-			var mergedSeries []Series
-			for mergedQuerier.Next() {
-				mergedSeries = append(mergedSeries, mergedQuerier.At())
-			}
-			testutil.Ok(t, mergedQuerier.Err())
-
-			for _, actualSeries := range mergedSeries {
+			merged, _, _ := NewMergeQuerier(qs[0], qs, ChainedSeriesMerge).Select(false, nil)
+			for merged.Next() {
 				testutil.Assert(t, tc.expected.Next(), "Expected Next() to be true")
+				actualSeries := merged.At()
 				expectedSeries := tc.expected.At()
 				testutil.Equals(t, expectedSeries.Labels(), actualSeries.Labels())
 
@@ -215,6 +207,7 @@ func TestMergeQuerierWithChainMerger(t *testing.T) {
 				testutil.Equals(t, expErr, actErr)
 				testutil.Equals(t, expSmpl, actSmpl)
 			}
+			testutil.Ok(t, merged.Err())
 			testutil.Assert(t, !tc.expected.Next(), "Expected Next() to be false")
 		})
 	}
diff --git a/storage/generic.go b/storage/generic.go
index d23e51a6c..a5a694cb2 100644
--- a/storage/generic.go
+++ b/storage/generic.go
@@ -108,24 +108,26 @@ func (q *chunkQuerierAdapter) Select(sortSeries bool, hints *SelectHints, matche
 
 type seriesMergerAdapter struct {
 	VerticalSeriesMergeFunc
+	buf []Series
 }
 
 func (a *seriesMergerAdapter) Merge(s ...Labels) Labels {
-	buf := make([]Series, 0, len(s))
+	a.buf = a.buf[:0]
 	for _, ser := range s {
-		buf = append(buf, ser.(Series))
+		a.buf = append(a.buf, ser.(Series))
 	}
-	return a.VerticalSeriesMergeFunc(buf...)
+	return a.VerticalSeriesMergeFunc(a.buf...)
 }
 
 type chunkSeriesMergerAdapter struct {
 	VerticalChunkSeriesMergerFunc
+	buf []ChunkSeries
 }
 
 func (a *chunkSeriesMergerAdapter) Merge(s ...Labels) Labels {
-	buf := make([]ChunkSeries, 0, len(s))
+	a.buf = a.buf[:0]
 	for _, ser := range s {
-		buf = append(buf, ser.(ChunkSeries))
+		a.buf = append(a.buf, ser.(ChunkSeries))
 	}
-	return a.VerticalChunkSeriesMergerFunc(buf...)
+	return a.VerticalChunkSeriesMergerFunc(a.buf...)
 }