diff --git a/blscosi/protocol/protocol.go b/blscosi/protocol/protocol.go
index 3d505ee00..8b7e740e0 100644
--- a/blscosi/protocol/protocol.go
+++ b/blscosi/protocol/protocol.go
@@ -104,9 +104,7 @@ func DefaultSubLeaders(nodes int) int {
 	if nodes == 1 {
 		return 1
 	}
-	// As `math.Pow` calculates `9 ** (1/2) < 3`,
-	// we add 0.0001 for the rounding error.
-	return int(math.Pow(float64(nodes-1), 1.0/2.0) + 0.0001)
+	return int(math.Pow(float64(nodes-1), 1.0/2.0))
 }
 
 // NewBlsCosi method is used to define the blscosi protocol.
diff --git a/blscosi/protocol/sub_protocol.go b/blscosi/protocol/sub_protocol.go
index 8a3eea761..a0ed1642d 100644
--- a/blscosi/protocol/sub_protocol.go
+++ b/blscosi/protocol/sub_protocol.go
@@ -4,6 +4,7 @@ import (
 	"crypto/rand"
 	"errors"
 	"fmt"
+	"golang.org/x/xerrors"
 	"sync"
 	"time"
 
@@ -207,8 +208,7 @@ func (p *SubBlsCosi) dispatchRoot() error {
 		case err := <-subLeaderActive:
 			if err != nil {
 				p.subleaderNotResponding <- true
-				log.Warnf("Couldn't contact subleader: %v", err)
-				return nil
+				return xerrors.Errorf("Couldn't contact subleader: %v", err)
 			}
 		case <-p.closeChan:
 			return nil
@@ -245,7 +245,17 @@ func (p *SubBlsCosi) dispatchSubLeader() error {
 		return err
 	}
 
-	p.sendToChildren(a)
+	if len(p.Children()) > 0 {
+		for _, node := range p.Children() {
+			go func(node *onet.TreeNode) {
+				err := p.SendTo(node, a)
+				if err != nil {
+					log.Warnf("Error while sending to leaf %s: %v",
+						node.Name(), err)
+				}
+			}(node)
+		}
+	}
 
 	responses := make(ResponseMap)
 	for _, c := range p.Children() {
@@ -447,16 +457,3 @@ func (p *SubBlsCosi) checkIntegrity() error {
 
 	return nil
 }
-
-// sendToChildren does not collect error messages,
-// but doesn't block on nodes with a non-rejecting firewall in front of them.
-func (p *SubBlsCosi) sendToChildren(msg interface{}) {
-	for _, c := range p.Children() {
-		go func(tn *onet.TreeNode) {
-			err := p.SendTo(tn, msg)
-			if err != nil {
-				log.Warnf("Error while sending to children: %v", err)
-			}
-		}(c)
-	}
-}
diff --git a/byzcoinx/byzcoinx_test.go b/byzcoinx/byzcoinx_test.go
index 5263e9007..8a45e0df0 100644
--- a/byzcoinx/byzcoinx_test.go
+++ b/byzcoinx/byzcoinx_test.go
@@ -200,7 +200,7 @@ func runProtocol(t *testing.T, nbrHosts int, nbrFault int, refuseIndex int, prot
 	log.Lvl3("Added counter", counters.size()-1, refuseIndex)
 
 	require.True(t, int(math.Pow(float64(bftCosiProto.nSubtrees),
-		3.0)) <= nbrHosts)
+		2.0)) <= nbrHosts)
 
 	// kill the leafs first
 	nbrFault = min(nbrFault, len(servers))
diff --git a/messaging/propagate.go b/messaging/propagate.go
index d53afc6ab..1f9b65da8 100644
--- a/messaging/propagate.go
+++ b/messaging/propagate.go
@@ -172,6 +172,7 @@ func (p *Propagate) Dispatch() error {
 	var gotSendData bool
 	var errs []error
 	subtreeCount := p.TreeNode().SubtreeCount()
+	errsChan := make(chan error, subtreeCount)
 
 	for process {
 		p.Lock()
@@ -207,7 +208,19 @@ func (p *Propagate) Dispatch() error {
 				process = false
 			}
 			log.Lvl3(p.ServerIdentity(), "Sending to children", p.Children())
-			p.sendToChildren(&msg.PropagateSendData)
+
+			// Just blindly send to the children - we don't care if they receive it or
+			// not. If they don't receive it, they will complain later.
+			for _, c := range p.Children() {
+				go func(tn *onet.TreeNode) {
+					err := p.SendTo(tn, &msg.PropagateSendData)
+					if err != nil {
+						log.Warnf("Error while sending to child %s: %v",
+							tn.Name(), err)
+						errsChan <- err
+					}
+				}(c)
+			}
 		case <-p.ChannelReply:
 			if !gotSendData {
 				log.Error("got response before send")
@@ -220,6 +233,11 @@ func (p *Propagate) Dispatch() error {
 					return err
 				}
 			}
+			errsChan <- nil
+		case err := <-errsChan:
+			if err != nil {
+				errs = append(errs, err)
+			}
 			// Only wait for the number of children that successfully received our message.
 			if received == subtreeCount-len(errs) && received >= subtreeCount-p.allowedFailures {
 				process = false
@@ -265,16 +283,3 @@ func (p *Propagate) Shutdown() error {
 	close(p.closing)
 	return nil
 }
-
-// sendToChildren does not collect error messages,
-// but doesn't block on nodes with a non-rejecting firewall in front of them.
-func (p *Propagate) sendToChildren(msg interface{}) {
-	for _, c := range p.Children() {
-		go func(tn *onet.TreeNode) {
-			err := p.SendTo(tn, msg)
-			if err != nil {
-				log.Warnf("Error while sending to children: %v", err)
-			}
-		}(c)
-	}
-}