diff --git a/slides/cours_11.md b/slides/cours_11.md
index 7e37204e4cabb0fd5be08f8ba6b7070ee73c7ad1..6f3c87563b41fd858222d1329955979ffd058428 100644
--- a/slides/cours_11.md
+++ b/slides/cours_11.md
@@ -247,7 +247,8 @@ void stack_pop(stack *s, int *val) {
 ```C
 void stack_destroy(stack *s) {
     while (!stack_is_empty(*s)) {
-        int val = stack_pop(s);
+        int val; 
+        stack_pop(s, &val);
     }
 }
 ```