diff --git a/crossfire/static-support.rkt b/crossfire/static-support.rkt
index 91b9f4b..ce490c6 100644
--- a/crossfire/static-support.rkt
+++ b/crossfire/static-support.rkt
@@ -115,6 +115,7 @@
         (fsync-call fd))))
 
   (define (port-fsync port)
+    (flush-output port)
     (match (system-type 'os)
       ['unix (port-fsync/unix port)]
       [x (error "don't know how to fsync on" x)]))