diff --git a/tools/libxl/libxl_uuid.c b/tools/libxl/libxl_uuid.c
index 7d4a032..996c08d 100644
--- a/tools/libxl/libxl_uuid.c
+++ b/tools/libxl/libxl_uuid.c
@@ -72,9 +72,9 @@ void libxl_uuid_generate(libxl_uuid *uuid)
 {
     uint32_t status;
 
-    BUILD_BUG_ON(sizeof(libxl_uuid) != sizeof(uuid_t));
     uuid_create(&uuid->uuid, &status);
     assert(status == uuid_s_ok);
+    uuid_enc_be(uuid->uuid_raw, &uuid->uuid);
 }
 
 #ifdef __FreeBSD__
@@ -85,6 +85,7 @@ int libxl_uuid_from_string(libxl_uuid *uuid, const char *in)
     uuid_from_string(in, &uuid->uuid, &status);
     if (status != uuid_s_ok)
         return -1;
+    uuid_enc_be(uuid->uuid_raw, &uuid->uuid);
     return 0;
 }
 #else
diff --git a/tools/libxl/libxl_uuid.h b/tools/libxl/libxl_uuid.h
index c5041c7..55e8d61 100644
--- a/tools/libxl/libxl_uuid.h
+++ b/tools/libxl/libxl_uuid.h
@@ -42,12 +42,12 @@ typedef struct {
 #include <stdio.h>
 #include <assert.h>
 
-typedef union {
+typedef struct {
     uuid_t uuid;
     uint8_t uuid_raw[16];
 } libxl_uuid;
 
-#define LIBXL_UUID_BYTES(arg) LIBXL__UUID_BYTES(arg.uuid_raw)
+#define LIBXL_UUID_BYTES(arg) LIBXL__UUID_BYTES(libxl_uuid_bytearray_const(&arg))
 
 #else