diff --git a/src/tree_data_helpers.c b/src/tree_data_helpers.c
index 86b0c64..905eadc 100644
--- a/src/tree_data_helpers.c
+++ b/src/tree_data_helpers.c
@@ -209,7 +209,7 @@
             node->flags |= LYD_WHEN_TRUE;
         } else {
             /* remember we need to evaluate this node's when */
-            ly_set_add(when_check, node, LY_SET_OPT_USEASLIST);
+            LY_CHECK_RET(ly_set_add(when_check, node, LY_SET_OPT_USEASLIST, NULL), );
         }
     }