diff --git a/arch/x86_64/pmap.c b/arch/x86_64/pmap.c
index e8c379f..2fff1b2 100644
--- a/arch/x86_64/pmap.c
+++ b/arch/x86_64/pmap.c
@@ -73,7 +73,7 @@ static pte_t make_pte(pfn_t pfn, vm_prot_t prot, page_size_t size)
 	}
 
 	if (!(prot & VM_PROT_EXEC)) {
-		v |= PTE_RW;
+		v |= PTE_NX;
 	}
 
 	if ((prot & VM_PROT_USER) && !(prot & VM_PROT_SVR)) {