diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -9292,6 +9292,11 @@
 		va = va_next;
 		for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; pte++,
 		    sva += PAGE_SIZE) {
+			/*
+			 * Avoid clearing the accessed bit for wired mappings.
+			 * Superpage demotion assumes that a wired mapping is
+			 * always accessed.
+			 */
 			if ((*pte & (PG_MANAGED | PG_V)) != (PG_MANAGED | PG_V))
 				goto maybe_invlrng;
 			else if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
@@ -9304,12 +9309,11 @@
 					m = PHYS_TO_VM_PAGE(*pte & PG_FRAME);
 					vm_page_dirty(m);
 				}
-				atomic_clear_long(pte, PG_M | PG_A);
-			} else if ((*pte & PG_A) != 0)
-				atomic_clear_long(pte, PG_A);
-			else
+			} else
 				goto maybe_invlrng;
 
+			atomic_clear_long(pte,
+			    PG_M | ((*pte & PG_W) == 0 ? PG_A : 0));
 			if ((*pte & PG_G) != 0) {
 				if (va == va_next)
 					va = sva;