diff --git a/tasks/mm0/include/file.h b/tasks/mm0/include/file.h
index 9330d69..f6d694a 100644
--- a/tasks/mm0/include/file.h
+++ b/tasks/mm0/include/file.h
@@ -17,5 +17,6 @@ int sys_read(l4id_t sender, int fd, void *buf, int count);
 int sys_write(l4id_t sender, int fd, void *buf, int count);
 int sys_lseek(l4id_t sender, int fd, off_t offset, int whence);
 
+#define vm_file_to_vnum(f)	(*(unsigned long *)((f)->priv_data))
 extern struct list_head vm_file_list;
 #endif /* __MM0_FILE_H__ */
diff --git a/tasks/mm0/include/vm_area.h b/tasks/mm0/include/vm_area.h
index 3bff25e..54ef3ad 100644
--- a/tasks/mm0/include/vm_area.h
+++ b/tasks/mm0/include/vm_area.h
@@ -130,7 +130,6 @@ struct vm_object {
 
 /* In memory representation of either a vfs file, a device. */
 struct vm_file {
-	unsigned long vnum;
 	unsigned long length;
 	unsigned int type;
 	struct list_head list;
diff --git a/tasks/mm0/src/file.c b/tasks/mm0/src/file.c
index 670c4c4..e2a486f 100644
--- a/tasks/mm0/src/file.c
+++ b/tasks/mm0/src/file.c
@@ -13,6 +13,7 @@
 #include <l4/api/kip.h>
 #include <posix/sys/types.h>
 #include <string.h>
+#include <file.h>
 
 /* List of all generic files */
 LIST_HEAD(vm_file_list);
@@ -92,7 +93,7 @@ int vfs_receive_sys_open(l4id_t sender, l4id_t opener, int fd,
 
 	/* Check if that vm_file is already in the list */
 	list_for_each_entry(vmfile, &vm_file_list, list) {
-		if (vmfile->vnum == vnum) {
+		if (vm_file_to_vnum(vmfile) == vnum) {
 			/* Add a reference to it from the task */
 			t->fd[fd].vmfile = vmfile;
 			vmfile->vm_obj.refcnt++;
@@ -105,7 +106,7 @@ int vfs_receive_sys_open(l4id_t sender, l4id_t opener, int fd,
 		return (int)vmfile;
 
 	/* Initialise and add it to global list */
-	vmfile->vnum = vnum;
+	vm_file_to_vnum(vmfile) = vnum;
 	vmfile->length = length;
 	vmfile->vm_obj.pager = &file_pager;
 	list_add(&vmfile->vm_obj.list, &vm_file_list);
@@ -172,7 +173,7 @@ int read_file_pages(struct vm_file *vmfile, unsigned long pfn_start,
 		if (IS_ERR(page)) {
 			printf("%s: %s:Could not read page %d "
 			       "from file with vnum: 0x%x\n", __TASKNAME__,
-			       __FUNCTION__, f_offset, vmfile->vnum);
+			       __FUNCTION__, f_offset, vm_file_to_vnum(vmfile));
 			return (int)page;
 		}
 	}
diff --git a/tasks/mm0/src/pagers.c b/tasks/mm0/src/pagers.c
index 1e01e3b..e2fbe9d 100644
--- a/tasks/mm0/src/pagers.c
+++ b/tasks/mm0/src/pagers.c
@@ -88,7 +88,8 @@ struct page *file_page_in(struct vm_object *vm_obj, unsigned long page_offset)
 		l4_map(paddr, vaddr, 1, MAP_USR_RW_FLAGS, VFS_TID);
 
 		/* Syscall to vfs to read into the page. */
-		if ((err = vfs_read(f->vnum, page_offset, 1, vaddr)) < 0)
+		if ((err = vfs_read(vm_file_to_vnum(f), page_offset,
+				    1, vaddr)) < 0)
 			goto out_err;
 
 		/* Unmap it from vfs */