diff --git a/gui-doc/scribblings/gui/style-delta-class.scrbl b/gui-doc/scribblings/gui/style-delta-class.scrbl
index c408aba77..77f8dae38 100644
--- a/gui-doc/scribblings/gui/style-delta-class.scrbl
+++ b/gui-doc/scribblings/gui/style-delta-class.scrbl
@@ -147,7 +147,7 @@ The family and face settings in a style delta are interdependent:
                        ([change-command (or/c 'change-size
                                               'change-bigger
                                               'change-smaller)]
-                        [v byte?])
+                        [v exact-integer?])
                        ([change-command (or/c 'change-underline
                                               'change-size-in-pixels)]
                         [v any/c]))]{