diff --git a/src/diff.c b/src/diff.c
index 2a72f85..257e18f 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -1470,8 +1470,8 @@
         LY_CHECK_RET(lyd_diff_change_op(diff_node, src_op));
 
         if (diff_cb) {
-            /* call callback */
-            LY_CHECK_RET(diff_cb(src_diff, diff_node, cb_data));
+            /* call callback with no source diff node since it was duplicated and just added */
+            LY_CHECK_RET(diff_cb(NULL, diff_node, cb_data));
         }
 
         /* update diff parent */
diff --git a/src/tree_data.h b/src/tree_data.h
index 65780d7..a48814d 100644
--- a/src/tree_data.h
+++ b/src/tree_data.h
@@ -1558,7 +1558,9 @@
  * @param[in,out] diff Target diff to merge into.
  * @param[in] src_diff Source diff.
  * @param[in] mod Module, whose diff only to consider, NULL for all modules.
- * @param[in] diff_cb Optional diff callback that will be called for every changed node.
+ * @param[in] diff_cb Optional diff callback that will be called for every merged node. Param @p diff_node is the source
+ * diff node while @p data_node is the updated target diff node. In case a whole subtree is added, the callback is
+ * called on the root with @p diff_node being NULL.
  * @param[in] cb_data Arbitrary callback data.
  * @param[in] options Bitmask of options flags, see @ref diffmergeoptions.
  * @return LY_SUCCESS on success,
@@ -1573,7 +1575,9 @@
  * @param[in,out] diff_first Target diff first sibling to merge into.
  * @param[in] diff_parent Target diff parent to merge into.
  * @param[in] src_sibling Source diff sibling to merge.
- * @param[in] diff_cb Optional diff callback that will be called for every changed node.
+ * @param[in] diff_cb Optional diff callback that will be called for every merged node. Param @p diff_node is the source
+ * diff node while @p data_node is the updated target diff node. In case a whole subtree is added, the callback is
+ * called on the root with @p diff_node being NULL.
  * @param[in] cb_data Arbitrary callback data.
  * @param[in] options Bitmask of options flags, see @ref diffmergeoptions.
  * @return LY_SUCCESS on success,