diff --git a/pkg/postage/service.go b/pkg/postage/service.go
index 7621e00d281..803daa3a66b 100644
--- a/pkg/postage/service.go
+++ b/pkg/postage/service.go
@@ -174,8 +174,8 @@ func (ps *service) GetStampIssuer(batchID []byte) (*StampIssuer, func() error, e
 
 // save persists the specified stamp issuer to the stamperstore.
 func (ps *service) save(st *StampIssuer) error {
-	st.bucketMtx.Lock()
-	defer st.bucketMtx.Unlock()
+	st.mtx.Lock()
+	defer st.mtx.Unlock()
 
 	if err := ps.store.Put(&StampIssuerItem{
 		Issuer: st,
diff --git a/pkg/postage/stamper.go b/pkg/postage/stamper.go
index 1ee16a8a133..a5f4107e375 100644
--- a/pkg/postage/stamper.go
+++ b/pkg/postage/stamper.go
@@ -11,7 +11,6 @@ import (
 	"github.com/ethersphere/bee/pkg/crypto"
 	"github.com/ethersphere/bee/pkg/storage"
 	"github.com/ethersphere/bee/pkg/swarm"
-	"resenje.org/multex"
 )
 
 var (
@@ -30,19 +29,18 @@ type stamper struct {
 	store  storage.Store
 	issuer *StampIssuer
 	signer crypto.Signer
-	mu     *multex.Multex
 }
 
 // NewStamper constructs a Stamper.
 func NewStamper(store storage.Store, issuer *StampIssuer, signer crypto.Signer) Stamper {
-	return &stamper{store, issuer, signer, multex.New()}
+	return &stamper{store, issuer, signer}
 }
 
 // Stamp takes chunk, see if the chunk can be included in the batch and
 // signs it with the owner of the batch of this Stamp issuer.
 func (st *stamper) Stamp(addr swarm.Address) (*Stamp, error) {
-	st.mu.Lock(addr.ByteString())
-	defer st.mu.Unlock(addr.ByteString())
+	st.issuer.mtx.Lock()
+	defer st.issuer.mtx.Unlock()
 
 	item := &StampItem{
 		BatchID:      st.issuer.data.BatchID,
diff --git a/pkg/postage/stampissuer.go b/pkg/postage/stampissuer.go
index 84b5292528a..bc3064580c0 100644
--- a/pkg/postage/stampissuer.go
+++ b/pkg/postage/stampissuer.go
@@ -151,8 +151,8 @@ func (s stampIssuerData) Clone() stampIssuerData {
 // A StampIssuer instance extends a batch with bucket collision tracking
 // embedded in multiple Stampers, can be used concurrently.
 type StampIssuer struct {
-	data      stampIssuerData
-	bucketMtx sync.Mutex
+	data stampIssuerData
+	mtx  sync.Mutex
 }
 
 // NewStampIssuer constructs a StampIssuer as an extension of a batch for local
@@ -177,10 +177,8 @@ func NewStampIssuer(label, keyID string, batchID []byte, batchAmount *big.Int, b
 
 // increment increments the count in the correct collision
 // bucket for a newly stamped chunk with given addr address.
+// Must be mutex locked before usage.
 func (si *StampIssuer) increment(addr swarm.Address) (batchIndex []byte, batchTimestamp []byte, err error) {
-	si.bucketMtx.Lock()
-	defer si.bucketMtx.Unlock()
-
 	bIdx := toBucket(si.BucketDepth(), addr)
 	bCnt := si.data.Buckets[bIdx]
 
@@ -263,8 +261,8 @@ func (si *StampIssuer) ImmutableFlag() bool {
 }
 
 func (si *StampIssuer) Buckets() []uint32 {
-	si.bucketMtx.Lock()
-	defer si.bucketMtx.Unlock()
+	si.mtx.Lock()
+	defer si.mtx.Unlock()
 	b := make([]uint32, len(si.data.Buckets))
 	copy(b, si.data.Buckets)
 	return b