diff --git a/headers/posix/termios.h b/headers/posix/termios.h
index ccf13ea7c2..451208aeea 100644
--- a/headers/posix/termios.h
+++ b/headers/posix/termios.h
@@ -106,11 +106,14 @@ struct termios {
 #define	B4800		0x0C
 #define	B9600		0x0D
 #define	B19200		0x0E
-#define	B31250		0x0F			/* for MIDI */
-#define B38400		0x10
-#define B57600		0x11
-#define B115200		0x12
-#define B230400		0x13
+#define B38400		0x0F
+#define B57600		0x10
+#define B115200		0x11
+#define B230400		0x12
+#define	B31250		0x13			/* for MIDI */
+	// Yes, this last one is out of order. Don't change it, it would break ABI.
+	// If you change it anyway, make sure the constants in SerialPort.h are
+	// matching.
 
 #define	CSIZE		0x20			/* character size */
 #define	CS5			0x00			/* only 7 and 8 bits supported */