diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index b0f0697bc69..677be26bc24 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -23,7 +23,7 @@ config SERIAL_SIGKILL_CHAR
 	int "Serial parse SIGKILL characters"
 	default 3 if SERIAL_CONSOLE
 	default 4 if !SERIAL_CONSOLE
-	depends on SIG_SIGKILL
+	depends on SIG_SIGKILL && BUILD_FLAT
 	---help---
 		Use ASCII 3 (Ctrl-c) or 4 (ctrl-d) inputs to determine whether to
 		send a SIGKILL event.  Other charcters may also be selected.
diff --git a/drivers/serial/serial.c b/drivers/serial/serial.c
index 494ce01beb7..892b77a2492 100644
--- a/drivers/serial/serial.c
+++ b/drivers/serial/serial.c
@@ -1371,6 +1371,8 @@ static int uart_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
 #endif
 
 #ifdef CONFIG_SERIAL_SIGKILL_CHAR
+          /* Make the given terminal the controlling terminal of the calling process */
+
           case TIOCSCTTY:
             {
               /* REVISIT:  This only applies to console devices (TTYs).  In