diff --git a/collects/2htdp/private/check-aux.ss b/collects/2htdp/private/check-aux.ss
index 88ee9bb973..b88d127a8c 100644
--- a/collects/2htdp/private/check-aux.ss
+++ b/collects/2htdp/private/check-aux.ss
@@ -41,8 +41,11 @@
 (define (internal-scene? i) 
   (and (= 0 (pinhole-x i)) (= 0 (pinhole-y i))))
 
-;; Number -> Integer
-(define (number->integer x)
+;; Number Symbol Symbol -> Integer
+(define (number->integer x . rst)
+  (define t (if (pair? rst) (car rst) ""))
+  (define p (if (and (pair? rst) (pair? (cdr rst))) (cadr rst) ""))
+  (check-arg t (and (number? x) (real? x)) "real number" p x)
   (inexact->exact (floor x)))
 
 ;; -----------------------------------------------------------------------------
@@ -160,7 +163,7 @@
 ;; Symbol Any String -> Void
 (define (check-pos t c r)
   (check-arg 
-   t (and (number? c) (>= (number->integer c) 0)) "positive integer" r c))
+   t (and (number? c) (>= (number->integer c t r) 0)) "positive integer" r c))
 
 ;; Symbol Any String String *-> Void
 (define (check-image tag i rank . other-message)
diff --git a/collects/2htdp/private/image.ss b/collects/2htdp/private/image.ss
index 7cea6fa228..0aeb932b0a 100644
--- a/collects/2htdp/private/image.ss
+++ b/collects/2htdp/private/image.ss
@@ -37,8 +37,8 @@
 
 (define (place-image image x y scene)
   (check-image 'place-image image "first")
-  (check-arg 'place-image (number? x) 'integer "second" x)
-  (check-arg 'place-image (number? y) 'integer "third" y)
+  (check-arg 'place-image (real? x) 'real "second" x)
+  (check-arg 'place-image (real? y) 'real "third" y)
   (check-scene 'place-image scene "fourth")
   (let ([x (number->integer x)]
         [y (number->integer y)])
@@ -55,14 +55,14 @@
 (define (scene+line img x0 y0 x1 y1 c)
   ;; img and c are checked via calls to add-line from image.ss
   (check-arg 'scene+line (scene? img) "scene" "first" "plain image")
-  (check-arg 'scene+line (number? x0) "number" "second" x0)
-  (check-arg 'scene+line (number? y0) "number" "third" y0)
-  (check-arg 'scene+line (number? x1) "number" "fourth" x1)
-  (check-arg 'scene+line (number? y1) "number" "fifth" y1)
-  (let ([x0 (number->integer x0)]
-        [x1 (number->integer x1)]
-        [y0 (number->integer y0)]
-        [y1 (number->integer y1)])
+  (check-arg 'scene+line (real? x0) "number" "second" x0)
+  (check-arg 'scene+line (real? y0) "number" "third" y0)
+  (check-arg 'scene+line (real? x1) "number" "fourth" x1)
+  (check-arg 'scene+line (real? y1) "number" "fifth" y1)
+  (let ([x0 (number->integer x0 'scene+line 'second)]
+        [x1 (number->integer x1 'scene+line 'third)]
+        [y0 (number->integer y0 'scene+line 'fourth)]
+        [y1 (number->integer y1 'scene+line 'fifth)])
     (add-line-to-scene0 img x0 y0 x1 y1 c)))
 
 ;; Image Number Number Image -> Image 
diff --git a/collects/2htdp/private/timer.ss b/collects/2htdp/private/timer.ss
index 1beaa18c30..1230cdcde2 100644
--- a/collects/2htdp/private/timer.ss
+++ b/collects/2htdp/private/timer.ss
@@ -30,7 +30,7 @@
            [timer (new timer% [notify-callback (lambda () (ptock))])])
     (define/override (start!)
       (unless (<= rate 0)
-        (send timer start (number->integer (* 1000 rate))))
+        (send timer start (number->integer (* 1000 rate) 'big-bang/universe 'clock-rate)))
       (super start!))
     (define/override (stop! w)
       (send timer stop)
diff --git a/collects/2htdp/universe.ss b/collects/2htdp/universe.ss
index 8cfa1be796..23ee7b5e5c 100644
--- a/collects/2htdp/universe.ss
+++ b/collects/2htdp/universe.ss
@@ -40,7 +40,9 @@
             except
             [(_ x rate) 
              #'(list (proc> 'on-tick (f2h x) 1) 
-                     (num> 'on-tick rate positive? "pos. number" "rate"))])]
+                     (num> 'on-tick rate (lambda (x)
+					   (and (real? x) (positive? x)))
+		       "pos. number" "rate"))])]
   ;; -- state specifies whether to display the current state 
   [state (expr-with-check bool> "expected a boolean (show state or not)")]
   ;; -- check-with must specify a predicate