diff --git a/sys/kern/kern_proc.c b/sys/kern/kern_proc.c
index 55f7e189e026..e45a4890fbe1 100644
--- a/sys/kern/kern_proc.c
+++ b/sys/kern/kern_proc.c
@@ -506,7 +506,6 @@ pgdelete(pgrp)
 	if (tp != NULL) {
 		tty_lock(tp);
 		tty_rel_pgrp(tp, pgrp);
-		tty_unlock(tp);
 	}
 
 	mtx_destroy(&pgrp->pg_mtx);
diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index bb0fb02c99f0..cd6a246f8fa1 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -940,10 +940,13 @@ tty_rel_free(struct tty *tp)
 void
 tty_rel_pgrp(struct tty *tp, struct pgrp *pg)
 {
+	MPASS(tp->t_sessioncnt > 0);
 	tty_lock_assert(tp, MA_OWNED);
 
 	if (tp->t_pgrp == pg)
 		tp->t_pgrp = NULL;
+	
+	tty_unlock(tp);
 }
 
 void