diff --git a/slides/cours_11.md b/slides/cours_11.md
index 322f83255718da3edec348877c98764bccaa89da..cda880c9714e523fde038ac69685b807a2d4c8be 100644
--- a/slides/cours_11.md
+++ b/slides/cours_11.md
@@ -248,7 +248,8 @@ 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);
     }
 }
 ```