diff --git a/pkgs/math-pkgs/math-lib/math/private/array/array-broadcast.rkt b/pkgs/math-pkgs/math-lib/math/private/array/array-broadcast.rkt
index 3401cd5efb..6a52fc2e9c 100644
--- a/pkgs/math-pkgs/math-lib/math/private/array/array-broadcast.rkt
+++ b/pkgs/math-pkgs/math-lib/math/private/array/array-broadcast.rkt
@@ -46,7 +46,7 @@
                    new-arr
                    (array-default-strict new-arr))]))
 
-(: shape-insert-axes (Indexes Fixnum -> Indexes))
+(: shape-insert-axes (Indexes Integer -> Indexes))
 (define (shape-insert-axes ds n)
   (vector-append ((inst make-vector Index) n 1) ds))