diff --git a/collects/tests/typed-racket/fail/non-portable-fixnum-singleton.rkt b/collects/tests/typed-racket/fail/non-portable-fixnum-singleton.rkt
new file mode 100644
index 0000000000..04cd1a0bbf
--- /dev/null
+++ b/collects/tests/typed-racket/fail/non-portable-fixnum-singleton.rkt
@@ -0,0 +1,8 @@
+#;
+(exn-pred exn:fail:syntax?)
+#lang typed/racket
+;; singleton types for values who runtime type depends is platform-dependent are unsafe
+;; PR13501
+(define: z : 10000000000000 10000000000000)
+
+(ann (if (and #t (fixnum? z)) z 0) (U 0 1))
diff --git a/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt b/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt
index bbd8ba6245..028c5c3f78 100644
--- a/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt
+++ b/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt
@@ -218,6 +218,15 @@
         (tc-e (min (ann -2 Negative-Fixnum) (ann 3 Fixnum)) -NegFixnum)
         (tc-e (min (ann 3 Fixnum) (ann -2 Negative-Fixnum)) -NegFixnum)
         (tc-e (exact->inexact (ann 3 Number)) (t:Un -InexactReal -InexactComplex))
+        (tc-err (let: ([z : 10000000000000 10000000000000]) z)) ; unsafe
+        (tc-err (let: ([z : -4611686018427387904 -4611686018427387904]) z)) ; unsafe
+        (tc-e (let: ([z : -4611686018427387905 -4611686018427387905]) z) (-val -4611686018427387905))
+        (tc-err (let: ([z : -1073741825 -1073741825]) z)) ; unsafe
+        (tc-e (let: ([z : -1073741824 -1073741824]) z) (-val -1073741824))
+        (tc-e (let: ([z : 268435455 268435455]) z) (-val 268435455))
+        (tc-err (let: ([z : 268435456 268435456]) z)) ; unsafe
+        (tc-err (let: ([z : 4611686018427387903 4611686018427387903]) z)) ; unsafe
+        (tc-e (let: ([z : 4611686018427387904 4611686018427387904]) z) (-val 4611686018427387904))
 
         [tc-e/t (lambda: () 3) (t:-> -PosByte : -true-lfilter)]
         [tc-e/t (lambda: ([x : Number]) 3) (t:-> N -PosByte : -true-lfilter)]
diff --git a/collects/typed-racket/private/parse-type.rkt b/collects/typed-racket/private/parse-type.rkt
index a63685b099..da404a3f7c 100644
--- a/collects/typed-racket/private/parse-type.rkt
+++ b/collects/typed-racket/private/parse-type.rkt
@@ -378,7 +378,23 @@
            [(Error:) Err]
            [_ Err]))]
       [t:atom
-       (-val (syntax-e #'t))]
+       ;; Integers in a "grey area", that is, integers whose runtime type is
+       ;; platform-dependent, cannot be safely assigned singleton types.
+       ;; Short story: (subtype (-val 10000000000000) -Fixnum) has no safe
+       ;;   answer. It's not a fixnum on 32 bits, and saying it's not a fixnum
+       ;;   causes issues with type-dead code detection.
+       ;; Long story: See email trail for PR13501 and #racket IRC logs from
+       ;;   Feb 11 2013.
+       (let ([val (syntax-e #'t)])
+         (when (and (exact-integer? val)
+                    ;; [min-64bit-fixnum, min-portable-fixnum)
+                    (or (and (>= val (- (expt 2 62)))
+                             (<  val (- (expt 2 30))))
+                        ;; (max-portable-index, max-64bit-fixnum]
+                        (and (>  val (sub1 (expt 2 28)))
+                             (<= val (sub1 (expt 2 62))))))
+           (tc-error "non-portable fixnum singleton types are not valid types: ~a" val))
+         (-val val))]
       [_ (tc-error "not a valid type: ~a" (syntax->datum stx))])))
 
 (define (parse-list-type stx)