diff --git a/lib/init-7.scm b/lib/init-7.scm
index 48e8a854..d631bd30 100644
--- a/lib/init-7.scm
+++ b/lib/init-7.scm
@@ -1375,7 +1375,10 @@
  (complex (define (real? x) (and (number? x) (not (%complex? x)))))
  (else (define real? number?)))
 (define (rational? x)
-  (and (real? x) (= x x) (not (= x (+ x (if (positive? x) 1 -1))))))
+  (and (real? x)
+       (if (or (> x 1) (< x -1))
+           (not (= x (/ x 2)))
+           (<= -1 x 1))))
 
 (define (eqv? a b) (if (eq? a b) #t (and (number? a) (equal? a b))))
 
diff --git a/tests/r7rs-tests.scm b/tests/r7rs-tests.scm
index 47db3165..258cecae 100644
--- a/tests/r7rs-tests.scm
+++ b/tests/r7rs-tests.scm
@@ -749,6 +749,9 @@
 (test #t (real? #e1e10))
 (test #t (real? +inf.0))
 (test #f (rational? -inf.0))
+(test #t (rational? 9007199254740991.0))
+(test #t (rational? 9007199254740992.0))
+(test #t (rational? 1.7976931348623157e308))
 (test #t (rational? 6/10))
 (test #t (rational? 6/3))
 (test #t (integer? 3+0i))