diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -1597,16 +1597,21 @@
 		}
 
 		/*
-		 * The page was left invalid.  Likely placed there by
+		 * If the page was left invalid, it was likely placed there by
 		 * an incomplete fault.  Just remove and ignore.
+		 *
+		 * One other possibility is that the map entry is wired, in
+		 * which case we must hang on to the page to avoid leaking it,
+		 * as the map entry owns the wiring.  This case can arise if the
+		 * backing pager is truncated.
 		 */
-		if (vm_page_none_valid(m)) {
+		if (vm_page_none_valid(m) && entry->wired_count == 0) {
 			if (vm_page_iter_remove(&pages, m))
 				vm_page_free(m);
 			continue;
 		}
 
-		/* vm_page_iter_rename() will dirty the page. */
+		/* vm_page_iter_rename() will dirty the page if it is valid. */
 		if (!vm_page_iter_rename(&pages, m, new_object, m->pindex -
 		    offidxstart)) {
 			vm_page_xunbusy(m);
diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -2038,15 +2038,10 @@
  *
  *	Panics if a page already resides in the new object at the new pindex.
  *
- *	Note: swap associated with the page must be invalidated by the move.  We
- *	      have to do this for several reasons:  (1) we aren't freeing the
- *	      page, (2) we are dirtying the page, (3) the VM system is probably
- *	      moving the page from object A to B, and will then later move
- *	      the backing store from A to B and we can't have a conflict.
- *
- *	Note: we *always* dirty the page.  It is necessary both for the
- *	      fact that we moved it, and because we may be invalidating
- *	      swap.
+ *	This routine dirties the page if it is valid, as callers are expected to
+ *	transfer backing storage only after moving the page.  Dirtying the page
+ *	ensures that the destination object retains the most recent copy of the
+ *	page.
  *
  *	The objects must be locked.
  */
@@ -2087,7 +2082,8 @@
 	m->object = new_object;
 
 	vm_page_insert_radixdone(m, new_object, mpred);
-	vm_page_dirty(m);
+	if (vm_page_any_valid(m))
+		vm_page_dirty(m);
 	vm_pager_page_inserted(new_object, m);
 	return (true);
 }