diff --git a/src/intervals.c b/src/intervals.c
index 75e37a8c90c..ee976fb1035 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -2333,6 +2333,9 @@ set_intervals_multibyte_1 (INTERVAL i, bool multi_flag,
 
   if (TOTAL_LENGTH (i) == 0)
     {
+      /* Delete the whole subtree.  */
+      i->left = NULL;
+      i->right = NULL;
       delete_interval (i);
       return;
     }