diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index f0ea75c18a5b..3344b35c281c 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -3845,7 +3845,8 @@ pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
 	pt_entry_t *pte, PG_G, PG_M, PG_RW, PG_V;
 	boolean_t anychanged, pv_lists_locked;
 
-	if ((prot & VM_PROT_READ) == VM_PROT_NONE) {
+	KASSERT((prot & ~VM_PROT_ALL) == 0, ("invalid prot %x", prot));
+	if (prot == VM_PROT_NONE) {
 		pmap_remove(pmap, sva, eva);
 		return;
 	}
diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c
index 2859b84b4582..37e14e9d62cf 100644
--- a/sys/i386/i386/pmap.c
+++ b/sys/i386/i386/pmap.c
@@ -3161,7 +3161,8 @@ pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
 	pt_entry_t *pte;
 	boolean_t anychanged, pv_lists_locked;
 
-	if ((prot & VM_PROT_READ) == VM_PROT_NONE) {
+	KASSERT((prot & ~VM_PROT_ALL) == 0, ("invalid prot %x", prot));
+	if (prot == VM_PROT_NONE) {
 		pmap_remove(pmap, sva, eva);
 		return;
 	}