diff --git a/src/tree_data_internal.h b/src/tree_data_internal.h
index 8b960d7..7a63e5f 100644
--- a/src/tree_data_internal.h
+++ b/src/tree_data_internal.h
@@ -360,6 +360,7 @@
 /**
  * @defgroup datahash Data nodes hash manipulation
  * @ingroup datatree
+ * @{
  */
 
 /**