diff --git a/Chains_across_the_Island/Fundamentals/double/double.c b/Chains_across_the_Island/Fundamentals/double/double.c
index e28e8a2..d17ec7a 100644
--- a/Chains_across_the_Island/Fundamentals/double/double.c
+++ b/Chains_across_the_Island/Fundamentals/double/double.c
@@ -11,7 +11,8 @@ struct dlist *dlist_append(struct dlist *l, int e)
     new_node->prev = NULL;
     new_node->next = l;
     new_node->data = e;
-    l->prev = new_node;
+
+    if (l) l->prev = new_node;
 
     return new_node;