diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index efe13ab366f4..8596b4dca945 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -80,7 +80,7 @@ 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,
 };