diff --git a/core/src/main/java/com/github/gumtreediff/tree/Tree.java b/core/src/main/java/com/github/gumtreediff/tree/Tree.java
index 9c060f6f5..e82aed2ac 100644
--- a/core/src/main/java/com/github/gumtreediff/tree/Tree.java
+++ b/core/src/main/java/com/github/gumtreediff/tree/Tree.java
@@ -57,7 +57,7 @@ public Tree(int type, String label) {
     }
 
     // Only used for cloning ...
-    private Tree(Tree other) {
+    protected Tree(Tree other) {
         this.type = other.type;
         this.label = other.getLabel();
         this.id = other.getId();