diff --git a/rate/rate.go b/rate/rate.go
index 12e813c..79a6bb6 100644
--- a/rate/rate.go
+++ b/rate/rate.go
@@ -125,7 +125,7 @@
 }
 
 // InfDuration is the duration returned by Delay when a Reservation is not OK.
-const InfDuration = time.Duration(1<<63 - 1)
+const InfDuration = time.Duration(math.MaxInt64)
 
 // DelayFrom returns the duration for which the reservation holder must wait
 // before taking the reserved action.  Zero duration means act immediately.