diff --git a/docs/man/xl.1.pod.in b/docs/man/xl.1.pod.in
index d4b5e8e362..0ec59a8b5c 100644
--- a/docs/man/xl.1.pod.in
+++ b/docs/man/xl.1.pod.in
@@ -1922,6 +1922,24 @@ shows the decimal value. For non-linear mode, it shows hexadecimal value.
 
 =back
 
+=head1 ENVIRONMENT
+
+=over 4
+
+=item B<LIBXL_DISK_BACKEND_UNTRUSTED>
+
+Set this environment variable to "1" to suggest to the guest that the disk
+backend shouldn't be trusted. If the variable is absent or set to "0", the
+backend will be trusted.
+
+=item B<LIBXL_NIC_BACKEND_UNTRUSTED>
+
+Set this environment variable to "1" to suggest to the guest that the network
+backend shouldn't be trusted. If the variable is absent or set to "0", the
+backend will be trusted.
+
+=back
+
 =head1 IGNORED FOR COMPATIBILITY WITH XM
 
 xl is mostly command-line compatible with the old xm utility used with
diff --git a/tools/libxl/libxl_disk.c b/tools/libxl/libxl_disk.c
index 64a6691424..fe4cb52811 100644
--- a/tools/libxl/libxl_disk.c
+++ b/tools/libxl/libxl_disk.c
@@ -246,6 +246,7 @@ static void device_disk_add(libxl__egc *egc, uint32_t domid,
     libxl_domain_config d_config;
     libxl_device_disk disk_saved;
     libxl__domain_userdata_lock *lock = NULL;
+    const char *envvar;
 
     libxl_domain_config_init(&d_config);
     libxl_device_disk_init(&disk_saved);
@@ -395,6 +396,10 @@ static void device_disk_add(libxl__egc *egc, uint32_t domid,
         flexarray_append(front, GCSPRINTF("%d", device->devid));
         flexarray_append(front, "device-type");
         flexarray_append(front, disk->is_cdrom ? "cdrom" : "disk");
+        flexarray_append(front, "trusted");
+        envvar = getenv("LIBXL_DISK_BACKEND_UNTRUSTED");
+        /* Set "trusted=1" if envvar missing or is "0". */
+        flexarray_append(front, !envvar || !strcmp("0", envvar) ? "1" : "0");
 
         /*
          * Old PV kernel disk frontends before 2.6.26 rely on tool stack to
diff --git a/tools/libxl/libxl_nic.c b/tools/libxl/libxl_nic.c
index 07880b39e1..b92281ab6a 100644
--- a/tools/libxl/libxl_nic.c
+++ b/tools/libxl/libxl_nic.c
@@ -129,6 +129,8 @@ static int libxl__set_xenstore_nic(libxl__gc *gc, uint32_t domid,
                                    flexarray_t *back, flexarray_t *front,
                                    flexarray_t *ro_front)
 {
+    const char *envvar;
+
     flexarray_grow(back, 2);
 
     if (nic->script)
@@ -237,6 +239,11 @@ static int libxl__set_xenstore_nic(libxl__gc *gc, uint32_t domid,
     flexarray_append(front, GCSPRINTF(
                                     LIBXL_MAC_FMT, LIBXL_MAC_BYTES(nic->mac)));
 
+    flexarray_append(front, "trusted");
+    envvar = getenv("LIBXL_NIC_BACKEND_UNTRUSTED");
+    /* Set "trusted=1" if envvar missing or is "0". */
+    flexarray_append(front, !envvar || !strcmp("0", envvar) ? "1" : "0");
+
     return 0;
 }