diff --git a/typed-racket-lib/typed-racket/base-env/base-env.rkt b/typed-racket-lib/typed-racket/base-env/base-env.rkt
index 2aea9dfc..8ee2af17 100644
--- a/typed-racket-lib/typed-racket/base-env/base-env.rkt
+++ b/typed-racket-lib/typed-racket/base-env/base-env.rkt
@@ -3001,7 +3001,7 @@
 [environment-variables-ref (-> -Environment-Variables -Bytes (-opt -Bytes))]
 [environment-variables-set! (->opt -Environment-Variables -Bytes (-opt -Bytes) [(-> Univ)] Univ)]
 [environment-variables-names (-> -Environment-Variables  (-lst -Bytes))]
-[string-environment-variable-name? (asym-pred Univ B (-PS (-is-type 0 -) -tt))]
+[string-environment-variable-name? (asym-pred Univ B (-PS (-is-type 0 -String) -tt))]
 [getenv (-> -String (Un -String (-val #f)))]
 [putenv (-> -String -String B)]