diff --git a/include/mmio.h b/include/mmio.h
index b72daca..313448e 100644
--- a/include/mmio.h
+++ b/include/mmio.h
@@ -38,6 +38,9 @@
 extern void mmio_write_32(uintptr_t addr, uint32_t value);
 extern uint32_t mmio_read_32(uintptr_t addr);
 
+extern void mmio_write_64(uintptr_t addr, uint64_t value);
+extern uint64_t mmio_read_64(uintptr_t addr);
+
 #endif /*__ASSEMBLY__*/
 
 #endif /* __MMIO_H__ */