diff --git a/scheme/rts/sleep.scm b/scheme/rts/sleep.scm
index 6c6e29e..f7ea628 100644
--- a/scheme/rts/sleep.scm
+++ b/scheme/rts/sleep.scm
@@ -7,7 +7,8 @@
     (disable-interrupts!)
     (enqueue-thread! queue (current-thread))
     (set! *dozers*
-	  (insert (cons (+ (real-time) n) queue)
+	  (insert (cons (+ (real-time) (inexact->exact (round n)))
+			queue)
 		  *dozers*
 		  (lambda (frob1 frob2)
 		    (< (car frob1) (car frob2)))))