diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index 98b6b099b1e1..4314fdadfa44 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -1011,8 +1011,8 @@ vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry)
 		while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
 		    lobject->type == OBJT_DEFAULT &&
 		    (backing_object = lobject->backing_object) != NULL) {
-			if (lobject->backing_object_offset & PAGE_MASK)
-				break;
+			KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
+			    0, ("vm_fault_prefault: unaligned object offset"));
 			pindex += lobject->backing_object_offset >> PAGE_SHIFT;
 			VM_OBJECT_LOCK(backing_object);
 			VM_OBJECT_UNLOCK(lobject);