diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 25f155205770..03c885d3640f 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -508,4 +508,8 @@ INIT_PER_CPU(irq_stack_backing_store);
            "fixed_percpu_data is not at start of per-cpu area");
 #endif
 
+#ifdef CONFIG_RETHUNK
+. = ASSERT((__x86_return_thunk & 0x3f) == 0, "__x86_return_thunk not cacheline-aligned");
+#endif
+
 #endif /* CONFIG_X86_64 */
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index b3b1e376dce8..3fd066d42ec0 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -143,7 +143,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  *    from re-poisioning the BTB prediction.
  */
 	.align 64
-	.skip 63, 0xcc
+	.skip 64 - (__x86_return_thunk - zen_untrain_ret), 0xcc
 SYM_START(zen_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	/*