diff --git a/src/lib-oauth2/oauth2-jwt.c b/src/lib-oauth2/oauth2-jwt.c
index afceda0a863..7911158263a 100644
--- a/src/lib-oauth2/oauth2-jwt.c
+++ b/src/lib-oauth2/oauth2-jwt.c
@@ -387,6 +387,7 @@ oauth2_jwt_copy_fields(ARRAY_TYPE(oauth2_field) *fields,
 
 			if (!json_node_is_singular(jnode)) {
 				root = array_append_space(&nodes);
+				subroot = array_front(&nodes);
 				root->root = json_tree_node_get_child(tnode);
 				root->array = json_node_is_array(jnode);
 				if (jnode->name == NULL)