diff --git a/lib/js/runtime.sx b/lib/js/runtime.sx
index d4f44c36..ecfd6c87 100644
--- a/lib/js/runtime.sx
+++ b/lib/js/runtime.sx
@@ -2291,8 +2291,13 @@
   (fn
     (v)
     (let
-      ((n (if (number? v) v (js-to-number v))))
-      (if (>= n 0) (floor n) (- 0 (floor (- 0 n)))))))
+      ((n (js-to-number v)))
+      (cond
+        ((js-number-is-nan n) 0)
+        ((= n (js-infinity-value)) 0)
+        ((= n (- 0 (js-infinity-value))) 0)
+        ((>= n 0) (floor n))
+        (else (- 0 (floor (- 0 n))))))))
 
 (define dict-has? (fn (d k) (contains? (keys d) k)))