https://svnweb.freebsd.org/ports/head/security/putty/files/patch-unix_uxpgnt.c?revision=496064&view=co

Index: unix/pageant.c
--- unix/pageant.c.orig
+++ unix/pageant.c
@@ -330,7 +330,7 @@ void pageant_fork_and_print_env(bool retain_tty)
         /* Get out of our previous process group, to avoid being
          * blasted by passing signals. But keep our controlling tty,
          * so we can keep checking to see if we still have one. */
-        setpgrp();
+        setpgrp(0, 0);
     } else {
         /* Do that, but also leave our entire session and detach from
          * the controlling tty (if any). */
