diff --git a/hw/timer/aspeed_timer.c b/hw/timer/aspeed_timer.c
index 745eb8608b..29cc5e8070 100644
--- a/hw/timer/aspeed_timer.c
+++ b/hw/timer/aspeed_timer.c
@@ -275,7 +275,11 @@ static void aspeed_timer_set_value(AspeedTimerCtrlState *s, int timer, int reg,
             int64_t delta = (int64_t) value - (int64_t) calculate_ticks(t, now);
             uint32_t rate = calculate_rate(t);
 
-            t->start += muldiv64(delta, NANOSECONDS_PER_SECOND, rate);
+            if (delta >= 0) {
+                t->start += muldiv64(delta, NANOSECONDS_PER_SECOND, rate);
+            } else {
+                t->start -= muldiv64(-delta, NANOSECONDS_PER_SECOND, rate);
+            }
             aspeed_timer_mod(t);
         }
         break;