Index: sys/fs/fuse/fuse_device.c
===================================================================
--- sys/fs/fuse/fuse_device.c
+++ sys/fs/fuse/fuse_device.c
@@ -89,6 +89,9 @@
 #include "fuse_internal.h"
 #include "fuse_ipc.h"
 
+#include <compat/linux/linux_errno.h>
+#include <compat/linux/linux_errno.inc>
+
 SDT_PROVIDER_DECLARE(fusefs);
 /* 
  * Fuse trace probe:
@@ -450,6 +453,15 @@
 	}
 	if ((err = uiomove(&ohead, sizeof(struct fuse_out_header), uio)) != 0)
 		return (err);
+
+	if (data->linux_errnos != 0 && ohead.error != 0) {
+		err = -ohead.error;
+		if (err < 0 || err >= sizeof(linux_to_bsd_errtbl))
+			return (EINVAL);
+
+		/* '-', because it will get flipped again below */
+		ohead.error = -linux_to_bsd_errtbl[err];
+	}
 
 	/*
 	 * We check header information (which is redundant) and compare it
Index: sys/fs/fuse/fuse_ipc.h
===================================================================
--- sys/fs/fuse/fuse_ipc.h
+++ sys/fs/fuse/fuse_ipc.h
@@ -217,6 +217,7 @@
 	struct selinfo			ks_rsel;
 
 	int				daemon_timeout;
+	int				linux_errnos;
 	unsigned			time_gran;
 	uint64_t			notimpl;
 	uint64_t			mnt_flag;
Index: sys/fs/fuse/fuse_vfsops.c
===================================================================
--- sys/fs/fuse/fuse_vfsops.c
+++ sys/fs/fuse/fuse_vfsops.c
@@ -300,6 +300,7 @@
 
 	uint64_t mntopts, __mntopts;
 	uint32_t max_read;
+	int linux_errnos;
 	int daemon_timeout;
 	int fd;
 
@@ -312,6 +313,7 @@
 
 	subtype = NULL;
 	max_read = ~0;
+	linux_errnos = 0;
 	err = 0;
 	mntopts = 0;
 	__mntopts = 0;
@@ -337,6 +339,7 @@
 	FUSE_FLAGOPT(intr, FSESS_INTR);
 
 	(void)vfs_scanopt(opts, "max_read=", "%u", &max_read);
+	(void)vfs_scanopt(opts, "linux_errnos", "%d", &linux_errnos);
 	if (vfs_scanopt(opts, "timeout=", "%u", &daemon_timeout) == 1) {
 		if (daemon_timeout < FUSE_MIN_DAEMON_TIMEOUT)
 			daemon_timeout = FUSE_MIN_DAEMON_TIMEOUT;
@@ -411,6 +414,7 @@
 	data->dataflags |= mntopts;
 	data->max_read = max_read;
 	data->daemon_timeout = daemon_timeout;
+	data->linux_errnos = linux_errnos;
 	data->mnt_flag = mp->mnt_flag & MNT_UPDATEMASK;
 	FUSE_UNLOCK();