diff --git a/hw/hpet.c b/hw/hpet.c
index 12bd64d8b1..6e6ea520bc 100644
--- a/hw/hpet.c
+++ b/hw/hpet.c
@@ -157,14 +157,14 @@ static inline uint64_t hpet_calculate_diff(HPETTimer *t, uint64_t current)
 
         cmp = (uint32_t)t->cmp;
         diff = cmp - (uint32_t)current;
-        diff = (int32_t)diff > 0 ? diff : (uint32_t)0;
+        diff = (int32_t)diff > 0 ? diff : (uint32_t)1;
         return (uint64_t)diff;
     } else {
         uint64_t diff, cmp;
 
         cmp = t->cmp;
         diff = cmp - current;
-        diff = (int64_t)diff > 0 ? diff : (uint64_t)0;
+        diff = (int64_t)diff > 0 ? diff : (uint64_t)1;
         return diff;
     }
 }