diff --git a/test-suite/tests/numbers.test b/test-suite/tests/numbers.test
index f20a37d93..459ae5072 100644
--- a/test-suite/tests/numbers.test
+++ b/test-suite/tests/numbers.test
@@ -50,7 +50,9 @@
 (define (documented? object)
   (not (not (object-documentation object))))
 
-(define fixnum-bit 30)
+(define fixnum-bit
+  (inexact->exact (+ (/ (log (+ most-positive-fixnum 1)) (log 2)) 1)))
+
 (define fixnum-min most-negative-fixnum)
 (define fixnum-max most-positive-fixnum)