diff --git a/tsdb/head.go b/tsdb/head.go
index 63d8e9ea1..692f7f77a 100644
--- a/tsdb/head.go
+++ b/tsdb/head.go
@@ -2079,7 +2079,7 @@ func newMemSeries(lset labels.Labels, id chunks.HeadSeriesRef, isolationDisabled
 		nextAt: math.MinInt64,
 	}
 	if !isolationDisabled {
-		s.txs = newTxRing(4)
+		s.txs = newTxRing(0)
 	}
 	return s
 }
diff --git a/tsdb/head_read.go b/tsdb/head_read.go
index 362764480..29f845c7b 100644
--- a/tsdb/head_read.go
+++ b/tsdb/head_read.go
@@ -682,7 +682,7 @@ func (s *memSeries) iterator(id chunks.HeadChunkID, c chunkenc.Chunk, isoState *
 
 		// Removing the extra transactionIDs that are relevant for samples that
 		// come after this chunk, from the total transactionIDs.
-		appendIDsToConsider := s.txs.txIDCount - (totalSamples - (previousSamples + numSamples))
+		appendIDsToConsider := int(s.txs.txIDCount) - (totalSamples - (previousSamples + numSamples))
 
 		// Iterate over the appendIDs, find the first one that the isolation state says not
 		// to return.
diff --git a/tsdb/head_test.go b/tsdb/head_test.go
index e30f16d46..83abeacbe 100644
--- a/tsdb/head_test.go
+++ b/tsdb/head_test.go
@@ -2552,7 +2552,7 @@ func TestIsolationAppendIDZeroIsNoop(t *testing.T) {
 
 	ok, _ := s.append(0, 0, 0, cOpts)
 	require.True(t, ok, "Series append failed.")
-	require.Equal(t, 0, s.txs.txIDCount, "Series should not have an appendID after append with appendID=0.")
+	require.Equal(t, 0, int(s.txs.txIDCount), "Series should not have an appendID after append with appendID=0.")
 }
 
 func TestHeadSeriesChunkRace(t *testing.T) {
diff --git a/tsdb/isolation.go b/tsdb/isolation.go
index e436884a8..86330f36e 100644
--- a/tsdb/isolation.go
+++ b/tsdb/isolation.go
@@ -240,8 +240,8 @@ func (i *isolation) closeAppend(appendID uint64) {
 // The transactionID ring buffer.
 type txRing struct {
 	txIDs     []uint64
-	txIDFirst int // Position of the first id in the ring.
-	txIDCount int // How many ids in the ring.
+	txIDFirst uint32 // Position of the first id in the ring.
+	txIDCount uint32 // How many ids in the ring.
 }
 
 func newTxRing(capacity int) *txRing {
@@ -251,21 +251,28 @@ func newTxRing(capacity int) *txRing {
 }
 
 func (txr *txRing) add(appendID uint64) {
-	if txr.txIDCount == len(txr.txIDs) {
+	if int(txr.txIDCount) == len(txr.txIDs) {
 		// Ring buffer is full, expand by doubling.
-		newRing := make([]uint64, txr.txIDCount*2)
+		newLen := txr.txIDCount * 2
+		if newLen == 0 {
+			newLen = 4
+		}
+		newRing := make([]uint64, newLen)
 		idx := copy(newRing, txr.txIDs[txr.txIDFirst:])
 		copy(newRing[idx:], txr.txIDs[:txr.txIDFirst])
 		txr.txIDs = newRing
 		txr.txIDFirst = 0
 	}
 
-	txr.txIDs[(txr.txIDFirst+txr.txIDCount)%len(txr.txIDs)] = appendID
+	txr.txIDs[int(txr.txIDFirst+txr.txIDCount)%len(txr.txIDs)] = appendID
 	txr.txIDCount++
 }
 
 func (txr *txRing) cleanupAppendIDsBelow(bound uint64) {
-	pos := txr.txIDFirst
+	if len(txr.txIDs) == 0 {
+		return
+	}
+	pos := int(txr.txIDFirst)
 
 	for txr.txIDCount > 0 {
 		if txr.txIDs[pos] < bound {
@@ -281,7 +288,7 @@ func (txr *txRing) cleanupAppendIDsBelow(bound uint64) {
 		}
 	}
 
-	txr.txIDFirst %= len(txr.txIDs)
+	txr.txIDFirst %= uint32(len(txr.txIDs))
 }
 
 func (txr *txRing) iterator() *txRingIterator {
@@ -296,7 +303,7 @@ func (txr *txRing) iterator() *txRingIterator {
 type txRingIterator struct {
 	ids []uint64
 
-	pos int
+	pos uint32
 }
 
 func (it *txRingIterator) At() uint64 {
@@ -305,7 +312,7 @@ func (it *txRingIterator) At() uint64 {
 
 func (it *txRingIterator) Next() {
 	it.pos++
-	if it.pos == len(it.ids) {
+	if int(it.pos) == len(it.ids) {
 		it.pos = 0
 	}
 }