diff --git a/src/main/java/azgracompress/kdtree/KDTreeBuilder.java b/src/main/java/azgracompress/kdtree/KDTreeBuilder.java
index 0f36c859c82b933eb9d864f8ad608cc2dc010388..7f0b5dbc4620ae60daaba24766bb2f9294c1c2aa 100644
--- a/src/main/java/azgracompress/kdtree/KDTreeBuilder.java
+++ b/src/main/java/azgracompress/kdtree/KDTreeBuilder.java
@@ -57,7 +57,7 @@ public class KDTreeBuilder {
      * @param featureVectors Feature vectors to build the tree with.
      * @return Node with its siblings.
      */
-    public KDNode buildTreeImpl(final int[][] featureVectors) {
+    private KDNode buildTreeImpl(final int[][] featureVectors) {
         if (featureVectors.length <= bucketSize) {
             return makeTerminalNode(featureVectors);
         }