diff --git a/collects/scribble/base.rkt b/collects/scribble/base.rkt
index 292d984034..0aed83450c 100644
--- a/collects/scribble/base.rkt
+++ b/collects/scribble/base.rkt
@@ -285,7 +285,7 @@
 
  [image (->* ((or/c path-string? (cons/c 'collects (listof bytes?))))
              (#:scale real?
-                      #:suffixes (listof #rx"^[.]"))
+                      #:suffixes (listof (and/c string? #rx"^[.]")))
              #:rest (listof content?)
              image-element?)])