diff --git a/esp8266/modmachine.c b/esp8266/modmachine.c
index 36872c9..80ae7ac 100644
--- a/esp8266/modmachine.c
+++ b/esp8266/modmachine.c
@@ -103,6 +103,8 @@
         }
     }
 
+    // prepare for RTC reset at wake up
+    rtc_prepare_deepsleep(sleep_us);
     // put the device in a deep-sleep state
     system_deep_sleep_set_option(0); // default power down mode; TODO check this
     system_deep_sleep(sleep_us);