diff --git a/slides/cours_12.md b/slides/cours_12.md
index 4146c0c2e5d1b205aff29087f4eb39e08fb4961d..c9646d2edda6c00afba9a4fa9a8d5e59728ddcc9 100644
--- a/slides/cours_12.md
+++ b/slides/cours_12.md
@@ -228,6 +228,8 @@ sorted_list sorted_list_extract(sorted_list list, int val) {
 
 # La recherche
 
+
+
 ```C
 element* sorted_list_search(sorted_list list, int val);
 ```
@@ -243,7 +245,7 @@ element* sorted_list_search(sorted_list list, int val) {
     element* pos = sorted_list_position(list, val); 
     if (NULL == pos && val == list->data) {
         return list; // first element contains val
-    } else if (NULL != pos->next && val == pos->next->data) {
+    } else if (NULL != pos && NULL != pos->next && val == pos->next->data) {
         return pos->next; // non-first element contains val
     } else {
         return NULL; // well... val's not here
@@ -277,7 +279,7 @@ element* sorted_list_position(sorted_list list, int val) {
     if (sorted_list_is_empty(list) || val <= list->data) {
         pos = NULL;
     } else {
-        while (NULL != pos->next && val > pos->next>data) {
+        while (NULL != pos->next && val > pos->next->data) {
             pos = pos->next;
         }
     }