diff --git a/lcthw-remnants-2/liblcthw/src/lcthw/list.c b/lcthw-remnants-2/liblcthw/src/lcthw/list.c
index bb7e354..de8483e 100644
--- a/lcthw-remnants-2/liblcthw/src/lcthw/list.c
+++ b/lcthw-remnants-2/liblcthw/src/lcthw/list.c
@@ -8,6 +8,8 @@ List *List_create()
 
 void List_destroy(List *list)
 {
+  List_validate(list);
+
   LIST_FOREACH(list, first, next, cur) {
     if(cur->prev) {
       free(cur->prev);
@@ -21,6 +23,8 @@ void List_destroy(List *list)
 
 void List_clear(List *list)
 {
+  List_validate(list);
+
   LIST_FOREACH(list, first, next, cur) {
     free(cur->value);
   }
@@ -29,13 +33,24 @@ void List_clear(List *list)
 
 void List_clear_destroy(List *list)
 {
-  List_clear(list);
-  List_destroy(list);
+  List_validate(list);
+
+  LIST_FOREACH(list, first, next, cur) {
+    free(cur->value);
+    if(cur->prev) {
+      free(cur->prev);
+    }
+  }
+
+  free(list->last);
+  free(list);
 }
 
 
 void List_push(List *list, void *value)
 {
+  List_validate(list);
+
   ListNode *node = calloc(1, sizeof(ListNode));
   check_mem(node);
 
@@ -58,12 +73,16 @@ error:
 
 void *List_pop(List *list)
 {
+  List_validate(list);
+
   ListNode *node = list->last;
   return node != NULL ? List_remove(list, node) : NULL;
 }
 
 void List_unshift(List *list, void *value)
 {
+  List_validate(list);
+
   ListNode *node = calloc(1, sizeof(ListNode));
   check_mem(node);
 
@@ -86,12 +105,16 @@ error:
 
 void *List_shift(List *list)
 {
+  List_validate(list);
+
   ListNode *node = list->first;
   return node != NULL ? List_remove(list, node) : NULL;
 }
 
 void *List_remove(List *list, ListNode *node)
 {
+  List_validate(list);
+
   void *result = NULL;
 
   check(list->first && list->last, "List is empty.");
diff --git a/lcthw-remnants-2/liblcthw/src/lcthw/list.h b/lcthw-remnants-2/liblcthw/src/lcthw/list.h
index 83fe51e..c7de1ab 100644
--- a/lcthw-remnants-2/liblcthw/src/lcthw/list.h
+++ b/lcthw-remnants-2/liblcthw/src/lcthw/list.h
@@ -2,6 +2,7 @@
 #define lcthw_List_h
 
 #include <stdlib.h>
+#include <assert.h>
 
 struct ListNode;
 
@@ -34,6 +35,9 @@ void *List_shift(List *list);
 
 void *List_remove(List *list, ListNode *node);
 
+#define List_validate(A) (assert(A != NULL && List_count(A) > -1 &&\
+      (List_count(A) > 0 && List_first(A) != NULL) && "invalid *List"))
+
 #define LIST_FOREACH(L, S, M, V) ListNode *_node = NULL;\
   ListNode *V = NULL;\
   for(V = _node = L->S; _node != NULL; V = _node = _node->M)