diff --git a/tasks/mm0/src/mmap.c b/tasks/mm0/src/mmap.c
index 6cdbea9..7bd2ac1 100644
--- a/tasks/mm0/src/mmap.c
+++ b/tasks/mm0/src/mmap.c
@@ -147,9 +147,10 @@ void *do_mmap(struct vm_file *mapfile, unsigned long file_offset,
 	      unsigned int flags, unsigned int npages)
 {
 	unsigned long map_pfn = __pfn(map_address);
+	unsigned long file_npages;
 	struct vm_area *new, *mapped;
 	struct vm_obj_link *vmo_link, *vmo_link2;
-	unsigned long file_npages;
+	int err;
 
 	/* Set up devzero if none given */
 	if (!mapfile) {
@@ -185,18 +186,12 @@ void *do_mmap(struct vm_file *mapfile, unsigned long file_offset,
 			return PTR_ERR(-EINVAL);
 		else if (!(map_address = mmap_new_address(task, flags, npages)))
 			return PTR_ERR(-ENOMEM);
-	} else {
-		/*
-		 * FIXME: Currently we don't allow overlapping vmas.
-		 * To be fixed soon. We need to handle intersection,
-		 * splitting, shrink/grow etc.
-		 */
-		list_for_each_entry(mapped, &task->vm_area_head->list, list)
-			BUG_ON(set_intersection(map_pfn, map_pfn + npages,
-						mapped->pfn_start,
-						mapped->pfn_end));
 	}
 
+	/* Unmap any existing vmas that overlap with the new mapping */
+	if ((err = do_munmap(task, map_address, npages)) < 0)
+		return PTR_ERR(err);
+
 	/* For valid regions that aren't allocated by us, create the vma. */
 	if (!(new = vma_new(__pfn(map_address), npages, flags, file_offset)))
 		return PTR_ERR(-ENOMEM);
diff --git a/tasks/mm0/src/munmap.c b/tasks/mm0/src/munmap.c
index 7ce5914..5f22a3c 100644
--- a/tasks/mm0/src/munmap.c
+++ b/tasks/mm0/src/munmap.c
@@ -133,7 +133,7 @@ int vma_flush_pages(struct vm_area *vma)
  * may span into zero or more vmas, and may involve shrinking, splitting
  * and destruction of multiple vmas.
  */
-int do_munmap(struct tcb *task, void *vaddr, unsigned long npages)
+int do_munmap(struct tcb *task, unsigned long vaddr, unsigned long npages)
 {
 	const unsigned long munmap_start = __pfn(vaddr);
 	const unsigned long munmap_end = munmap_start + npages;
@@ -167,10 +167,11 @@ int do_munmap(struct tcb *task, void *vaddr, unsigned long npages)
 int sys_munmap(struct tcb *task, void *start, unsigned long length)
 {
 	/* Must be aligned on a page boundary */
-	if ((unsigned long)start & PAGE_MASK)
+	if (!is_page_aligned(start))
 		return -EINVAL;
 
-	return do_munmap(task, start, __pfn(page_align_up(length)));
+	return do_munmap(task, (unsigned long)start,
+			 __pfn(page_align_up(length)));
 }