diff --git a/core/installer/cluster.go b/core/installer/cluster.go
index 9ac89da..19220af 100644
--- a/core/installer/cluster.go
+++ b/core/installer/cluster.go
@@ -167,8 +167,8 @@
 		if err != nil {
 			return "", err
 		}
-		if v, ok := cfg.Proxies[src]; ok || v != dst {
-			return "", fmt.Errorf("wrong mapping %s already exists (%s)", src, v)
+		if v, ok := cfg.Proxies[src]; !ok || v != dst {
+			return "", fmt.Errorf("wrong mapping from source: %s actual: %s expected: %s", src, v, dst)
 		}
 		delete(cfg.Proxies, src)
 		w, err := fs.Writer(c.NginxConfigPath)