diff --git a/abstract-machine/klib/include/klib-macros.h b/abstract-machine/klib/include/klib-macros.h
index d943b06..1f7c370 100644
--- a/abstract-machine/klib/include/klib-macros.h
+++ b/abstract-machine/klib/include/klib-macros.h
@@ -17,7 +17,7 @@
 
 #define io_read(reg) \
   ({ reg##_T __io_param; \
-    ioe_read(reg, (void*)&__io_param); \
+    ioe_read(reg, &__io_param); \
     __io_param; })
 
 #define io_write(reg, ...) \
diff --git a/nemu/src/device/timer.c b/nemu/src/device/timer.c
index 2aff819..98ced99 100644
--- a/nemu/src/device/timer.c
+++ b/nemu/src/device/timer.c
@@ -23,8 +23,8 @@ static void rtc_io_handler(uint32_t offset, int len, bool is_write) {
   assert(offset == 0 || offset == 4);
   if (!is_write && offset == 4) {
     uint64_t us = get_time();
-    rtc_port_base[0] = (uint32_t)us;
-    rtc_port_base[1] = us >> 32;
+    ((volatile uint32_t*)rtc_port_base)[0] = (uint32_t)us;
+    ((volatile uint32_t*)rtc_port_base)[1] = us >> 32;
   }
 }