diff --git a/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt b/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt
index 225de0e400..aa69f11471 100644
--- a/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt
+++ b/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt
@@ -1086,6 +1086,7 @@
         (tc-e (symbol-interned? (string->unreadable-symbol "bar")) B)
         (tc-e (symbol-interned? (string->uninterned-symbol "bar")) B)
         (tc-e (symbol-interned? (gensym 'foo)) B)
+        (tc-e (symbol-interned? (gensym "foo")) B)
 
         (tc-e (symbol-unreadable? (gensym)) B)
         (tc-e (symbol-unreadable? 'foo) B)
diff --git a/collects/typed-racket/base-env/base-env.rkt b/collects/typed-racket/base-env/base-env.rkt
index 51e61fd3f9..89095d1f4a 100644
--- a/collects/typed-racket/base-env/base-env.rkt
+++ b/collects/typed-racket/base-env/base-env.rkt
@@ -389,7 +389,7 @@
 [string->symbol (-String . -> . Sym)]
 [string->uninterned-symbol (-String . -> . Sym)]
 [string->unreadable-symbol (-String . -> . Sym)]
-[gensym (->opt [Sym] Sym)]
+[gensym (->opt [(Un Sym -String)] Sym)]