diff --git a/abstract-machine/am/src/platform/nemu/ioe/timer.c b/abstract-machine/am/src/platform/nemu/ioe/timer.c
index a22c539..a566162 100644
--- a/abstract-machine/am/src/platform/nemu/ioe/timer.c
+++ b/abstract-machine/am/src/platform/nemu/ioe/timer.c
@@ -17,7 +17,10 @@ void __am_timer_init() {
 }
 
 void __am_timer_uptime(AM_TIMER_UPTIME_T *uptime) {
-  (*(volatile AM_TIMER_UPTIME_T *)uptime).us = GET_TIME() - __timer_start;
+  volatile uint32_t lower_timer = inl(RTC_ADDR);
+  volatile uint32_t high_timer = inl(RTC_ADDR + 4);
+  volatile uint64_t timer = lower_timer + (((uint64_t) high_timer) << 32);
+  (*(volatile AM_TIMER_UPTIME_T *)uptime).us = timer - __timer_start;
   PNT_BITS(uptime->us);
 }