diff --git a/stack.c b/stack.c
index 35e7708..1309122 100644
--- a/stack.c
+++ b/stack.c
@@ -69,14 +69,11 @@ StackNode *pop(StackNode *stack) {
 void *top(StackNode *stack) { return stack != NULL ? stack->data : NULL; }
 
 // Clears stack and releases all memory.
-StackNode *clearStack(StackNode *stack) {
+void clearStack(StackNode **stack) {
 
-  while (stack != NULL) {
-
-    StackNode *next = stack->next;
-    free(stack);
-    stack = next;
+  while (*stack != NULL) {
+    StackNode *next = (*stack)->next;
+    free(*stack);
+    *stack = next;
   }
-
-  return NULL;
 }
\ No newline at end of file
diff --git a/stack.h b/stack.h
index f90d217..bbb3fce 100644
--- a/stack.h
+++ b/stack.h
@@ -13,6 +13,7 @@ typedef struct StackNode {
 
   void *data;
   struct StackNode *next;
+  struct StackNode *prev;
 
 } StackNode;
 
@@ -29,6 +30,6 @@ StackNode *pop(StackNode *stack);
 void *top(StackNode *stack);
 
 // Clears stack and releases all memory.
-StackNode *clearStack(StackNode *stack);
+void clearStack(StackNode **stack);
 
 #endif
diff --git a/test_stack.c b/test_stack.c
index 52ff263..78b019b 100644
--- a/test_stack.c
+++ b/test_stack.c
@@ -31,12 +31,13 @@ void test_clearStack(void) {
   int testInts[] = {1, 2, 3, 4, 5};
   StackNode *testStack = NULL;
 
+  // Stack füllen
   for (int i = 0; i < 5; i++) {
-
     testStack = push(testStack, &testInts[i]);
   }
 
-  testStack = clearStack(testStack);
+  clearStack(&testStack);
+
   TEST_ASSERT_NULL(testStack);
 }