diff --git a/libnetwork/osl/neigh_linux.go b/libnetwork/osl/neigh_linux.go
index e875f6ab64..c881f5df48 100644
--- a/libnetwork/osl/neigh_linux.go
+++ b/libnetwork/osl/neigh_linux.go
@@ -147,7 +147,9 @@ func (n *networkNamespace) AddNeighbor(dstIP net.IP, dstMac net.HardwareAddr, op
 		return fmt.Errorf("could not add neighbor entry: %v", err)
 	}
 
+	n.Lock()
 	n.neighbors = append(n.neighbors, nh)
+	n.Unlock()
 
 	return nil
 }