diff --git a/collects/tests/syntax-color/scribble-lexer.rkt b/collects/tests/syntax-color/scribble-lexer.rkt
index 98c3758733..f94aa561d4 100644
--- a/collects/tests/syntax-color/scribble-lexer.rkt
+++ b/collects/tests/syntax-color/scribble-lexer.rkt
@@ -23,12 +23,12 @@
                                    (caddar l)))
                          (loop (+ (+ pos (caar l))) (cdr l)))))])
     (unless (equal? v val)
-      (printf "FAILED, line ~s\n" line)
-      (printf " result\n")
-      (pretty-print v)
-      (printf " is not expected\n")
-      (pretty-print val)
-      (printf "\n"))))
+      (eprintf "FAILED, line ~s\n" line)
+      (eprintf " result\n")
+      (pretty-print v (current-error-port))
+      (eprintf " is not expected\n")
+      (pretty-print val (current-error-port))
+      (eprintf "\n"))))
 
 (define-syntax-rule (test str len-val)
   (test* str len-val (syntax-line #'str)))