diff -pNaru5 trueport-6.10.0.orig/ptyx/ptys.c trueport-6.10.0/ptyx/ptys.c
--- trueport-6.10.0.orig/ptyx/ptys.c	2020-05-28 07:56:32.000000000 -0400
+++ trueport-6.10.0/ptyx/ptys.c	2021-08-10 15:09:44.904120804 -0400
@@ -487,10 +487,14 @@ static void ptyx_slave_start(struct tty_
 //        changing the state of a terminal when we are not a process
 //        in the forground.  See tty_io.c
 // 
 //*****************************************************************************
 
+#if LINUX_VERSION_CODE >=  KERNEL_VERSION(5,10,180)
+int tty_check_change(struct tty_struct *tty);
+#endif
+
 #if (LINUX_VERSION_CODE <  KERNEL_VERSION(2,6,39))		// Less than 2.6.39
 static int ptyx_slave_ioctl(struct tty_struct *tty, struct file *file,
 									unsigned int cmd, unsigned long arg)
 #else
 static int ptyx_slave_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)