diff --git a/pycardium/modules/utime.c b/pycardium/modules/utime.c
index 88fe86b9ad2933d1f5e109e0113cf24453be69d3..6a61a7e79f0336b423cc2f5b233584c3852465cd 100644
--- a/pycardium/modules/utime.c
+++ b/pycardium/modules/utime.c
@@ -46,7 +46,7 @@ static mp_obj_t time_time_ms(void)
 {
 	uint64_t milliseconds;
 	milliseconds = epic_rtc_get_milliseconds() -
-		       (EPOCH_OFFSET + TZONE_OFFSET) * 1000ULL;
+		       EPOCH_OFFSET * 1000ULL + TZONE_OFFSET * 1000ULL;
 	return mp_obj_new_int_from_ull(milliseconds);
 }
 MP_DEFINE_CONST_FUN_OBJ_0(time_time_ms_obj, time_time_ms);