diff --git a/caddy.go b/caddy.go
index a29f05d7..d2f60001 100644
--- a/caddy.go
+++ b/caddy.go
@@ -858,6 +858,7 @@ func Stop() error {
 	for {
 		instancesMu.Lock()
 		if len(instances) == 0 {
+			instancesMu.Unlock()
 			break
 		}
 		inst := instances[0]