diff --git a/libifupdown/dict.c b/libifupdown/dict.c
index a0b5f2a..3dea682 100644
--- a/libifupdown/dict.c
+++ b/libifupdown/dict.c
@@ -14,6 +14,7 @@
  * from the use of this software.
  */
 
+#include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 #include "libifupdown/dict.h"
@@ -55,14 +56,22 @@ lif_dict_add_once(struct lif_dict *dict, const char *key, void *data,
                   int (*compar)(const void *, const void *))
 {
 	struct lif_list *existing = lif_dict_find_all(dict, key);
-	if (existing)
+	if (existing != NULL)
 	{
+		bool found = false;
 		struct lif_node *iter;
 		LIF_LIST_FOREACH(iter, existing->head)
 		{
 			if (!compar(data, iter->data))
-				return NULL;
+			{
+				found = true;
+				break;
+			}
 		}
+
+		lif_list_free_nodes (&existing);
+		if (found)
+			return NULL;
 	}
 
 	struct lif_dict_entry *entry = calloc(1, sizeof *entry);
diff --git a/libifupdown/list.c b/libifupdown/list.c
index 6a44f86..6b92b1c 100644
--- a/libifupdown/list.c
+++ b/libifupdown/list.c
@@ -3,6 +3,7 @@
  * Purpose: linked lists
  *
  * Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
+ * Copyright (c) 2020 Maximilian Wilhelm <max@sdn.clinic>
  *
  * Permission to use, copy, modify, and/or distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -14,8 +15,26 @@
  */
 
 #include <stdint.h>
+#include <stdlib.h>
 #include "libifupdown/list.h"
 
+void
+lif_list_free_nodes(struct lif_list **list)
+{
+	if (*list == NULL)
+		return;
+
+	struct lif_node *iter;
+
+	LIF_LIST_FOREACH (iter, (*list)->head)
+	{
+		free (iter->prev);
+	}
+
+	free (iter);
+	free (*list);
+}
+
 void
 lif_node_insert(struct lif_node *node, void *data, struct lif_list *list)
 {
diff --git a/libifupdown/list.h b/libifupdown/list.h
index 326eca0..a0155d6 100644
--- a/libifupdown/list.h
+++ b/libifupdown/list.h
@@ -3,6 +3,7 @@
  * Purpose: linked lists
  *
  * Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
+ * Copyright (c) 2020 Maximilian Wilhelm <max@sdn.clinic>
  *
  * Permission to use, copy, modify, and/or distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -29,6 +30,8 @@ struct lif_list {
 	size_t length;
 };
 
+extern void lif_list_free_nodes(struct lif_list **list);
+
 extern void lif_node_insert(struct lif_node *node, void *data, struct lif_list *list);
 extern void lif_node_insert_tail(struct lif_node *node, void *data, struct lif_list *list);
 extern void lif_node_delete(struct lif_node *node, struct lif_list *list);