diff --git a/collects/typed-racket/optimizer/tool/report.rkt b/collects/typed-racket/optimizer/tool/report.rkt
index 0fcae2626f..907421f507 100644
--- a/collects/typed-racket/optimizer/tool/report.rkt
+++ b/collects/typed-racket/optimizer/tool/report.rkt
@@ -32,18 +32,44 @@
     (generate-log this))))
 
 
+(define (log-output in done-chan)
+  (let loop ()
+    (sync (handle-evt
+           (read-line-evt in 'linefeed)
+           (lambda (line)
+             (cond [(eof-object? line) (channel-put done-chan 'done)]
+                   [else
+                    (log-warning
+                     (format "Optimization Coach Program Output: ~a" line))
+                    (loop)]))))))
+
 (define (run-inside-optimization-coach-sandbox this thunk)
   (call-with-trusted-sandbox-configuration
    (lambda ()
-     (define port-name (send this get-port-name))
-     (parameterize ([current-namespace (make-base-namespace)]
-                    [current-load-relative-directory
-                     (if (path-string? port-name)
-                         (let-values ([(base name _) (split-path port-name)])
-                           base)
-                         (current-load-relative-directory))]
-                    [read-accept-reader #t])
-       (thunk)))))
+     (define port-name  (send this get-port-name))
+     ;; If the sandboxed program produces any output, log it as `warning'.
+     ;; Mimics what check-syntax does.
+     (define log-output? (log-level? (current-logger) 'warning))
+     (define-values (log-in log-out)
+       (if log-output? (make-pipe) (values #f (open-output-nowhere))))
+     (define log-done-chan (make-channel))
+     (when log-output? (thread (lambda () (log-output log-in log-done-chan))))
+     ;; Set up the environment.
+     (begin0
+         (parameterize
+             ([current-namespace (make-base-namespace)]
+              [current-load-relative-directory
+               (if (path-string? port-name)
+                   (let-values ([(base name _) (split-path port-name)])
+                     base)
+                   (current-load-relative-directory))]
+              [read-accept-reader #t]
+              [current-output-port log-out]
+              [current-error-port  log-out])
+           (thunk))
+       (when log-output?
+         (close-output-port log-out)
+         (sync log-done-chan))))))
 
 (define (generate-log this)
   (define portname (send this get-port-name))