diff --git a/typed-racket-lib/typed-racket/base-env/base-env-numeric.rkt b/typed-racket-lib/typed-racket/base-env/base-env-numeric.rkt
index aa0773a6..aa269fd8 100644
--- a/typed-racket-lib/typed-racket/base-env/base-env-numeric.rkt
+++ b/typed-racket-lib/typed-racket/base-env/base-env-numeric.rkt
@@ -132,20 +132,17 @@
   (define fx--type
     (lambda ()
       (fx-from-cases
-       (binop -Zero)
-       (map (lambda (t) (commutative-binop t -Zero t))
-            (list -One -PosByte -Byte -PosIndex -Index))
+       (-> -Int -Zero -Fixnum : -true-filter : (-arg-path 0))
        (-One -One . -> . -Zero)
        (-PosByte -One . -> . -Byte)
        (-PosIndex -One . -> . -Index)
-       (-PosFixnum -One . -> . -NonNegFixnum)
        (-PosInt -One . -> . -NonNegFixnum)
        (-NegInt -Nat . -> . -NegFixnum)
        (-NonPosInt -PosInt . -> . -NegFixnum)
        (-NonPosInt -Nat . -> . -NonPosFixnum)
-       (-PosInt -NonPosInt . -> . -PosInt)
-       (-Nat -NegInt . -> . -PosInt)
-       (-Nat -NonPosInt . -> . -Nat)
+       (-PosInt -NonPosInt . -> . -PosFixnum)
+       (-Nat -NegInt . -> . -PosFixnum)
+       (-Nat -NonPosInt . -> . -NonNegFixnum)
        (-Int -Int . -> . -Fixnum))))
   (define fx*-type
     (lambda ()