diff --git a/js-assembler/check-valid-module-source.rkt b/js-assembler/check-valid-module-source.rkt
index 9301788..3914232 100644
--- a/js-assembler/check-valid-module-source.rkt
+++ b/js-assembler/check-valid-module-source.rkt
@@ -42,7 +42,7 @@
                      (lambda (exn)
                        ;; We can't even get the bytecode for the file.
                        ;; Fail immediately.
-                       (printf "ERROR: Can't read a Racket module from ~e.  The file may be ill-formed.\n"
+                       (printf "ERROR: Can't read a Racket module from ~e.  The file may be ill-formed or be written in a language that Whalesong doesn't recognize.\n"
                                module-source-path)
                        (printf "\nFor reference, the error message produced when trying to read ~e is:\n\n" module-source-path)
                        (printf "~a\n" (exn-message exn))