Index: sys/vm/vm_map.c
===================================================================
--- sys/vm/vm_map.c
+++ sys/vm/vm_map.c
@@ -491,8 +491,6 @@
 	pmap_activate(curthread);
 
 	/* Remove the daemon's reference to the old address space. */
-	KASSERT(oldvm->vm_refcnt > 1,
-	    ("vmspace_switch_aio: oldvm dropping last reference"));
 	vmspace_free(oldvm);
 }