diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index 7bbc924..726c543 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -26,7 +26,7 @@
 #include "libxl.h"
 #include "libxl_internal.h"
 
-const char *string_of_kinds[] = {
+static const char *string_of_kinds[] = {
     [DEVICE_VIF] = "vif",
     [DEVICE_VBD] = "vbd",
     [DEVICE_TAP] = "tap",
@@ -45,6 +45,9 @@ int libxl_device_generic_add(struct libxl_ctx *ctx, libxl_device *device,
     struct xs_permissions backend_perms[2];
     struct xs_permissions hotplug_perms[1];
 
+    if (!is_valid_device_kind(device->backend_kind) || !is_valid_device_kind(device->kind))
+        return ERROR_INVAL;
+
     dom_path_backend = libxl_xs_get_dompath(ctx, device->backend_domid);
     dom_path = libxl_xs_get_dompath(ctx, device->domid);
 
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 11698bc..34f2e38 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -68,7 +68,7 @@ typedef enum {
     DEVICE_CONSOLE,
 } libxl_device_kinds;
 
-extern const char *string_of_kinds[];
+#define is_valid_device_kind(kind) (((kind) >= DEVICE_VIF) && ((kind) <= DEVICE_CONSOLE))
 
 typedef struct {
     uint32_t backend_devid;