diff --git a/libnetwork/sandbox.go b/libnetwork/sandbox.go
index 775b92ab31..4367518d70 100644
--- a/libnetwork/sandbox.go
+++ b/libnetwork/sandbox.go
@@ -147,7 +147,7 @@ func (sb *sandbox) Key() string {
 
 func (sb *sandbox) Labels() map[string]interface{} {
 	sb.Lock()
-	sb.Unlock()
+	defer sb.Unlock()
 	opts := make(map[string]interface{}, len(sb.config.generic))
 	for k, v := range sb.config.generic {
 		opts[k] = v