diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 2b3c10f00a7e..aa2013346adb 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -4973,7 +4973,7 @@ pmap_demote_DMAP(vm_paddr_t base, vm_size_t len, boolean_t invalidate)
 	KASSERT(powerof2(len), ("pmap_demote_DMAP: len is not a power of 2"));
 	KASSERT((base & (len - 1)) == 0,
 	    ("pmap_demote_DMAP: base is not a multiple of len"));
-	if (len < NBPDP) {
+	if (len < NBPDP && base < dmaplimit) {
 		va = PHYS_TO_DMAP(base);
 		changed = FALSE;
 		PMAP_LOCK(kernel_pmap);