diff --git a/unpack.c b/unpack.c
index a0f79b0..36313c9 100644
--- a/unpack.c
+++ b/unpack.c
@@ -266,19 +266,19 @@ dump_content_set (struct node *content_sets, struct stack *head,
 		  struct stack *tail)
 {
 	int i;
-	struct stack stack;
-	stack.prev = tail;
-	tail->next = &stack;
+	static struct stack stk;
+	stk.prev = tail;
+	tail->next = &stk;
 
 	for (i = 0; i < content_sets->count; i++) {
-		stack.path = content_sets->paths[i];
-		dump_content_set(content_sets->children[i], head, &stack);
+		stk.path = content_sets->paths[i];
+		dump_content_set(content_sets->children[i], head, &stk);
 	}
 
 	if (content_sets->count == 0) {
 		struct stack *cur = head;
 
-		for (cur = head->next; cur != &stack; cur = cur->next) {
+		for (cur = head->next; cur != &stk; cur = cur->next) {
 			printf("/%s", cur->path);
 		}
 		printf("\n");
@@ -288,11 +288,11 @@ dump_content_set (struct node *content_sets, struct stack *head,
 static void
 dump_content_sets (struct node *content_sets)
 {
-	struct stack stack;
-	stack.next = NULL;
-	stack.path = NULL;
+	static struct stack stk;
+	stk.next = NULL;
+	stk.path = NULL;
 
-	dump_content_set (content_sets, &stack, &stack);
+	dump_content_set (content_sets, &stk, &stk);
 }
 
 static void
@@ -300,12 +300,12 @@ count_content_set (struct node *content_sets, struct stack *head,
 		   struct stack *tail, int *count)
 {
 	int i;
-	struct stack stack;
-	tail->next = &stack;
+	static struct stack stk;
+	tail->next = &stk;
 
 	for (i = 0; i < content_sets->count; i++) {
-		stack.path = content_sets->paths[i];
-		count_content_set(content_sets->children[i], head, &stack,
+		stk.path = content_sets->paths[i];
+		count_content_set(content_sets->children[i], head, &stk,
 				  count);
 	}
 
@@ -317,11 +317,11 @@ count_content_set (struct node *content_sets, struct stack *head,
 static void
 count_content_sets (struct node *content_sets, int *count)
 {
-	struct stack stack;
-	stack.next = NULL;
-	stack.path = NULL;
+	static struct stack stk;
+	stk.next = NULL;
+	stk.path = NULL;
 
-	count_content_set (content_sets, &stack, &stack, count);
+	count_content_set (content_sets, &stk, &stk, count);
 }
 
 static void