diff --git a/arch/x86_64/include/mango/machine/pmap.h b/arch/x86_64/include/mango/machine/pmap.h
index f501702..8d47179 100644
--- a/arch/x86_64/include/mango/machine/pmap.h
+++ b/arch/x86_64/include/mango/machine/pmap.h
@@ -3,6 +3,8 @@
 
 #include <arch/paging.h>
 
+#define ML_PMAP_INVALID ((uintptr_t)-1)
+
 typedef pml4t_ptr_t ml_pmap_t;
 typedef uint64_t ml_pfn_t;