Create Treenode with malloc in C

Question

I have troubles creating the rootnode of an Binary Search Tree.

I defined the node in the headerfile bst.h:

#ifndef BST_H_
#define BST_H_

struct BST
{
  int data;            /* data contained at root */
  struct BST *left; /* left node */
  struct BST *right; /* right node */
};

typedef struct BST BST;

BST * bst_new (int data);

#endif /* BST_H_ */

Here is the bst.c file :

#include "stdafx.h"
#include "bst.h"
#include <stdio.h>

BST* bst_new(int data)
{
    BST *new_node = (BST*)malloc(sizeof(BST));
    if (new_node == NULL)
    {
        fprintf(stderr, "Out of memory!!! (create_node)\n");
        exit(1);
    }
    new_node->data = data;
    new_node->left = NULL;
    new_node->right = NULL;
    return new_node;
}

And now i try to create the Rootnode of the BST with:

#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <time.h>

#include "bst.h"


int main ()
{
    /* create new tree */
    BST *bst = bst_new(10);

    return 0;
}

But i get an Error in bst.c saying that i make an "Write access violation" in line "new_node->data = data;". How can i get this thing working?