diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 5036104d5470..2375f5f4f763 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -79,7 +79,7 @@ static struct desc_struct startup_gdt[GDT_ENTRIES] = {
  * while the kernel still uses a direct mapping.
  */
 static struct desc_ptr startup_gdt_descr = {
-	.size = sizeof(startup_gdt),
+	.size = sizeof(startup_gdt)-1,
 	.address = 0,
 };