diff --git a/week3/stack.c b/week3/stack.c
index 1c5d66d..dfc2fd8 100644
--- a/week3/stack.c
+++ b/week3/stack.c
@@ -102,6 +102,7 @@ void DisplayStack(Stack *stack) {
 
 void DestroyStack(Stack *stack) {
 	free(stack->data);
+	stack->data = NULL;
 	stack->size = 0;
 	stack->top = -1;
 }