Index: sys/vm/vm_map.c
===================================================================
--- sys/vm/vm_map.c
+++ sys/vm/vm_map.c
@@ -2824,9 +2824,6 @@
 			continue;
 		}
 
-		if (obj->type != OBJT_DEFAULT &&
-		    (obj->flags & OBJ_SWAP) == 0)
-			continue;
 		VM_OBJECT_WLOCK(obj);
 		if (obj->type != OBJT_DEFAULT &&
 		    (obj->flags & OBJ_SWAP) == 0) {
@@ -4139,7 +4136,13 @@
 		 */
 		size = src_entry->end - src_entry->start;
 		if ((src_object = src_entry->object.vm_object) != NULL) {
+			/*
+			 * Swap-backed objects need special handling.  Note that
+			 * this is an unlocked check, so it is possible to race
+			 * with an OBJT_DEFAULT -> OBJT_SWAP conversion.
+			 */
 			if (src_object->type == OBJT_DEFAULT ||
+			    src_object->type == OBJT_SWAP ||
 			    (src_object->flags & OBJ_SWAP) != 0) {
 				vm_map_copy_swap_object(src_entry, dst_entry,
 				    size, fork_charge);
Index: sys/vm/vm_mmap.c
===================================================================
--- sys/vm/vm_mmap.c
+++ sys/vm/vm_mmap.c
@@ -1368,9 +1368,8 @@
 			goto done;
 		}
 	} else {
-		KASSERT(obj->type == OBJT_DEFAULT ||
-		    (obj->flags & OBJ_SWAP) != 0,
-		    ("wrong object type"));
+		KASSERT(obj->type == OBJT_DEFAULT || obj->type == OBJT_SWAP ||
+		    (obj->flags & OBJ_SWAP) != 0, ("wrong object type"));
 		vm_object_reference(obj);
 #if VM_NRESERVLEVEL > 0
 		if ((obj->flags & OBJ_COLORED) == 0) {
Index: sys/vm/vm_pageout.c
===================================================================
--- sys/vm/vm_pageout.c
+++ sys/vm/vm_pageout.c
@@ -1886,8 +1886,9 @@
 		if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 &&
 		    obj->ref_count != 1)
 			continue;
-		if (obj->type == OBJT_DEFAULT || obj->type == OBJT_PHYS ||
-		    obj->type == OBJT_VNODE || (obj->flags & OBJ_SWAP) != 0)
+		if (obj->type == OBJT_DEFAULT || obj->type == OBJT_SWAP ||
+		    obj->type == OBJT_PHYS || obj->type == OBJT_VNODE ||
+		    (obj->flags & OBJ_SWAP) != 0)
 			res += obj->resident_page_count;
 	}
 	return (res);