diff --git a/timespans/accountlock.go b/timespans/accountlock.go
index 76757a000..43aa0a7b9 100644
--- a/timespans/accountlock.go
+++ b/timespans/accountlock.go
@@ -18,6 +18,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>
 
 package timespans
 
+import (
+	"sync"
+)
+
 var AccLock *AccountLock
 
 func init() {
@@ -26,6 +30,7 @@ func init() {
 
 type AccountLock struct {
 	queue map[string]chan bool
+	sync.Mutex
 }
 
 func NewAccountLock() *AccountLock {
@@ -33,11 +38,13 @@ func NewAccountLock() *AccountLock {
 }
 
 func (cm *AccountLock) GuardGetCost(name string, handler func() (*CallCost, error)) (reply *CallCost, err error) {
+	cm.Lock()
 	lock, exists := AccLock.queue[name]
 	if !exists {
 		lock = make(chan bool, 1)
 		AccLock.queue[name] = lock
 	}
+	cm.Unlock()
 	lock <- true
 	reply, err = handler()
 	<-lock
diff --git a/timespans/accountlock_test.go b/timespans/accountlock_test.go
new file mode 100644
index 000000000..69100a1ab
--- /dev/null
+++ b/timespans/accountlock_test.go
@@ -0,0 +1,47 @@
+/*
+Rating system designed to be used in VoIP Carriers World
+Copyright (C) 2012  Radu Ioan Fericean
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>
+*/
+
+package timespans
+
+import (
+	"testing"
+	"time"
+	"log"
+)
+
+func TestAccountLock(t *testing.T) {
+	go AccLock.Guard("1", func() (float64, error) {
+		log.Print("first 1")
+		time.Sleep(1 * time.Second)
+		log.Print("end first 1")
+		return 0, nil
+	})
+	go AccLock.Guard("2", func() (float64, error) {
+		log.Print("first 2")
+		time.Sleep(1 * time.Second)
+		log.Print("end first 2")
+		return 0, nil
+	})
+	go AccLock.Guard("1", func() (float64, error) {
+		log.Print("second 1")
+		time.Sleep(1 * time.Second)
+		log.Print("end second 1")
+		return 0, nil
+	})
+	time.Sleep(3 * time.Second)
+}