diff --git a/tests/server/sockfilt.c b/tests/server/sockfilt.c
index 34eb20b990..38015e22fb 100644
--- a/tests/server/sockfilt.c
+++ b/tests/server/sockfilt.c
@@ -1087,6 +1087,10 @@ int main(int argc, char *argv[])
 #ifdef WIN32
   win32_init();
   atexit(win32_cleanup);
+
+  setmode(fileno(stdin), O_BINARY);
+  setmode(fileno(stdout), O_BINARY);
+  setmode(fileno(stderr), O_BINARY);
 #endif
 
   install_signal_handlers();