diff --git a/_web_server/playground-server.scm b/_web_server/playground-server.scm
index 3ca83be..cf5c64f 100755
--- a/_web_server/playground-server.scm
+++ b/_web_server/playground-server.scm
@@ -459,14 +459,20 @@
           (vvp (string-trim (or (option-get opts "vvp-exe") "vvp")))
           (iverilog (string-trim (or (option-get opts "iverilog-exe") "iverilog"))))
 
-      (if (option-get opts "help")
-          (begin
-            (print-help (car args))
-            (exit -1))
-          (begin
-            (printlog "Listen on '~a' port '~a'" addr port)
-            (printlog "Server URL: '~a/~a'" host root)
+      (cond
+       (err
+        (display (format "Unknown option '~a'\n" err))
+        (print-help (car args))
+        (exit -1))
 
-            (run-server
-             (make-page-handler host root INDEX-FILE vvp iverilog)
-             'http `(#:host ,addr #:port ,port)))))))
+       ((option-get opts "help")
+        (print-help (car args))
+        (exit -1))
+
+       (else
+        (printlog "Listen on '~a' port '~a'" addr port)
+        (printlog "Server URL: '~a/~a'" host root)
+
+        (run-server
+         (make-page-handler host root INDEX-FILE vvp iverilog)
+         'http `(#:host ,addr #:port ,port)))))))