Index: head/sys/compat/linux/linux_ioctl.h
===================================================================
--- head/sys/compat/linux/linux_ioctl.h
+++ head/sys/compat/linux/linux_ioctl.h
@@ -278,6 +278,7 @@
 #define	LINUX_SOUND_MIXER_WRITE_LINE1	0x4d0E
 #define	LINUX_SOUND_MIXER_WRITE_LINE2	0x4d0F
 #define	LINUX_SOUND_MIXER_WRITE_LINE3	0x4d10
+#define	LINUX_SOUND_MIXER_WRITE_MONITOR	0x4d18
 #define	LINUX_SOUND_MIXER_INFO		0x4d65
 #define	LINUX_OSS_GETVERSION		0x4d76
 #define	LINUX_SOUND_MIXER_READ_STEREODEVS	0x4dfb
Index: head/sys/compat/linux/linux_ioctl.c
===================================================================
--- head/sys/compat/linux/linux_ioctl.c
+++ head/sys/compat/linux/linux_ioctl.c
@@ -1794,6 +1794,10 @@
 		args->cmd = SETDIR(SOUND_MIXER_WRITE_LINE3);
 		return (sys_ioctl(td, (struct ioctl_args *)args));
 
+	case LINUX_SOUND_MIXER_WRITE_MONITOR:
+		args->cmd = SETDIR(SOUND_MIXER_WRITE_MONITOR);
+		return (sys_ioctl(td, (struct ioctl_args *)args));
+
 	case LINUX_SOUND_MIXER_INFO: {
 		/* Key on encoded length */
 		switch ((args->cmd >> 16) & 0x1fff) {