diff --git a/omci_sim.go b/omci_sim.go
index 6cc0708..a792911 100644
--- a/omci_sim.go
+++ b/omci_sim.go
@@ -51,9 +51,11 @@
 	}).Tracef("Processing OMCI pakcet")
 
 	key := OnuKey{intfId, onuId}
+	OnuOmciStateMapLock.Lock()
 	if _, ok := OnuOmciStateMap[key]; !ok {
 		OnuOmciStateMap[key] = NewOnuOmciState()
 	}
+	OnuOmciStateMapLock.Unlock()
 
 	if _, ok := Handlers[msgType]; !ok {
 		log.WithFields(log.Fields{
@@ -111,4 +113,4 @@
 	}).Tracef("OMCI-SIM Response")
 
 	return resp, nil
-}
\ No newline at end of file
+}