diff --git a/blockchain/skipchain/db.go b/blockchain/skipchain/db.go
index fda62a0c9..faf65b5b5 100644
--- a/blockchain/skipchain/db.go
+++ b/blockchain/skipchain/db.go
@@ -82,6 +82,9 @@ func (db *InMemoryDatabase) Write(block SkipBlock) error {
 // Contains implements skipchain.Database. It returns true if the block is
 // stored in the database, otherwise false.
 func (db *InMemoryDatabase) Contains(index uint64) bool {
+	db.Lock()
+	defer db.Unlock()
+
 	return index < uint64(len(db.blocks))
 }
 
diff --git a/blockchain/skipchain/ops.go b/blockchain/skipchain/ops.go
index e07c9d5a1..102054f4d 100644
--- a/blockchain/skipchain/ops.go
+++ b/blockchain/skipchain/ops.go
@@ -15,7 +15,7 @@ import (
 	"golang.org/x/xerrors"
 )
 
-const catchUpLeeway = 200 * time.Millisecond
+const catchUpLeeway = 100 * time.Millisecond
 
 // operations implements helper functions that can be used by the handlers for
 // common operations.
@@ -95,7 +95,7 @@ func (ops *operations) catchUp(target SkipBlock, addr mino.Address) error {
 		from = last.GetIndex() + 1
 	}
 
-	if target.GetIndex()-from <= 2 {
+	if target.GetIndex()-from <= 1 {
 		// When only one block is missing, that probably means the propagation
 		// is not yet over, so it gives a chance to wait for it before starting
 		// the actual catch up.
@@ -191,12 +191,16 @@ func (ops *operations) waitBlock(index uint64) {
 	ops.watcher.Add(observer)
 	defer ops.watcher.Remove(observer)
 
-	select {
-	case <-observer.ch:
-		return
-	case <-time.After(catchUpLeeway):
-		// Even if the commit message could arrive later, the catch up procedure
-		// starts anyway.
-		return
+	for {
+		select {
+		case block := <-observer.ch:
+			if block.GetIndex() == index {
+				return
+			}
+		case <-time.After(catchUpLeeway):
+			// Even if the commit message could arrive later, the catch up procedure
+			// starts anyway.
+			return
+		}
 	}
 }
diff --git a/blockchain/skipchain/ops_test.go b/blockchain/skipchain/ops_test.go
index 789982b41..b81102da4 100644
--- a/blockchain/skipchain/ops_test.go
+++ b/blockchain/skipchain/ops_test.go
@@ -81,19 +81,19 @@ func TestOperations_CatchUp(t *testing.T) {
 		ops.db = &fakeDatabase{blocks: []SkipBlock{{}, {}, {}}}
 		ops.catchUpLock.Unlock()
 	}()
-	err = ops.catchUp(SkipBlock{Index: 3, BackLink: hash}, fake.NewAddress(0))
+	err = ops.catchUp(SkipBlock{Index: 2, BackLink: hash}, fake.NewAddress(0))
 	require.NoError(t, err)
 	require.Equal(t, 2, call.Len())
 
 	// Catch up with only one block missing but it arrives during the catch up.
 	ops.db = &fakeDatabase{blocks: []SkipBlock{{}}}
 	ops.watcher = &fakeWatcher{call: call, block: SkipBlock{}}
-	err = ops.catchUp(SkipBlock{Index: 3, BackLink: hash}, fake.NewAddress(0))
+	err = ops.catchUp(SkipBlock{Index: 2, BackLink: hash}, fake.NewAddress(0))
 	require.NoError(t, err)
 	require.Equal(t, 4, call.Len())
 
 	ops.db = &fakeDatabase{blocks: []SkipBlock{{}}, err: xerrors.New("oops")}
-	err = ops.catchUp(SkipBlock{Index: 3}, nil)
+	err = ops.catchUp(SkipBlock{Index: 2}, nil)
 	require.EqualError(t, err, "couldn't read last block: oops")
 
 	ops.db = &fakeDatabase{blocks: []SkipBlock{{}}}
diff --git a/consensus/cosipbft/mod.go b/consensus/cosipbft/mod.go
index aa4aae235..b61a79907 100644
--- a/consensus/cosipbft/mod.go
+++ b/consensus/cosipbft/mod.go
@@ -139,6 +139,8 @@ func (c *Consensus) Store(in consensus.Chain) error {
 			if err != nil {
 				return xerrors.Errorf("couldn't store link: %v", err)
 			}
+
+			c.queue.Clear()
 		}
 	}
 
diff --git a/consensus/cosipbft/mod_test.go b/consensus/cosipbft/mod_test.go
index ccd2b6797..f3ba09079 100644
--- a/consensus/cosipbft/mod_test.go
+++ b/consensus/cosipbft/mod_test.go
@@ -179,6 +179,7 @@ func TestConsensus_Store(t *testing.T) {
 	cons := &Consensus{
 		encoder: encoding.NewProtoEncoder(),
 		storage: newInMemoryStorage(),
+		queue:   fakeQueue{},
 	}
 
 	links := []forwardLink{
@@ -585,6 +586,10 @@ type fakeQueue struct {
 	err error
 }
 
+func (q fakeQueue) Clear() {
+
+}
+
 func (q fakeQueue) Finalize(to Digest, commit crypto.Signature) (*ForwardLinkProto, error) {
 	return &ForwardLinkProto{}, q.err
 }
diff --git a/consensus/cosipbft/queue.go b/consensus/cosipbft/queue.go
index 8d20820f3..2a8d9b9f9 100644
--- a/consensus/cosipbft/queue.go
+++ b/consensus/cosipbft/queue.go
@@ -16,6 +16,7 @@ type Queue interface {
 	New(fl forwardLink, authority crypto.CollectiveAuthority) error
 	LockProposal(to Digest, sig crypto.Signature) error
 	Finalize(to Digest, sig crypto.Signature) (*ForwardLinkProto, error)
+	Clear()
 }
 
 type item struct {
@@ -148,3 +149,10 @@ func (q *queue) Finalize(to Digest, sig crypto.Signature) (*ForwardLinkProto, er
 
 	return packed.(*ForwardLinkProto), nil
 }
+
+func (q *queue) Clear() {
+	q.Lock()
+	q.locked = false
+	q.items = nil
+	q.Unlock()
+}
diff --git a/ledger/inventory/mem/mod.go b/ledger/inventory/mem/mod.go
index 6ac8b32cc..5ea7c53bf 100644
--- a/ledger/inventory/mem/mod.go
+++ b/ledger/inventory/mem/mod.go
@@ -2,6 +2,7 @@ package mem
 
 import (
 	"bytes"
+	"encoding/binary"
 	"fmt"
 	"sort"
 	"sync"
@@ -134,6 +135,10 @@ func (inv *InMemoryInventory) Stage(f func(inventory.WritablePage) error) (inven
 func (inv *InMemoryInventory) computeHash(page *inMemoryPage) error {
 	h := inv.hashFactory.New()
 
+	buffer := make([]byte, 8)
+	binary.LittleEndian.PutUint64(buffer, page.index)
+	h.Write(buffer)
+
 	keys := make(DigestSlice, 0, len(page.entries))
 	for key := range page.entries {
 		keys = append(keys, key)