diff --git a/scribble-lib/scribble/eval.rkt b/scribble-lib/scribble/eval.rkt
index 7c41aac2..2df5beba 100644
--- a/scribble-lib/scribble/eval.rkt
+++ b/scribble-lib/scribble/eval.rkt
@@ -44,7 +44,7 @@
             (-> any/c any)]
 
            [scribble-exn->string
-            (-> any/c string?)]
+            (parameter/c (-> any/c string?))]
            [scribble-eval-handler
             (parameter/c (-> (-> any/c any) boolean? any/c any))]
            [make-log-based-eval
diff --git a/scribble-test/tests/scribble/example.rkt b/scribble-test/tests/scribble/example.rkt
index 1e7ec167..be26d0ea 100644
--- a/scribble-test/tests/scribble/example.rkt
+++ b/scribble-test/tests/scribble/example.rkt
@@ -32,10 +32,27 @@
   (check-exn blames-this-module?
     (λ () (make-eval-factory '() #:lang '(+ 2 2))))
 
+  (check-exn blames-this-module?
+    (λ () (scribble-exn->string #f)))
+  (check-exn blames-this-module?
+    (λ () (scribble-exn->string (λ (a b c) a))))
+  (check-not-exn
+    (λ () (scribble-exn->string)))
+  (check-not-exn
+    (λ ()
+      (parameterize ((scribble-exn->string (λ (a) "hello")))
+        ((scribble-exn->string) "error"))))
+
   (check-exn blames-this-module?
     (λ () (scribble-eval-handler #f)))
   (check-exn blames-this-module?
     (λ () (scribble-eval-handler (λ (ev t) t))))
+  (check-not-exn
+    (λ () (scribble-eval-handler)))
+  (check-not-exn
+    (λ ()
+      (parameterize ((scribble-eval-handler (λ (a b c) c)))
+        ((scribble-eval-handler) (λ (x) x) #f #true))))
 
   (check-exn blames-this-module?
     (λ () (make-log-based-eval #f 'record)))