diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
index 746df8e69f..2f5ce1826b 100644
--- a/xen/include/public/arch-arm.h
+++ b/xen/include/public/arch-arm.h
@@ -218,7 +218,7 @@ typedef uint64_t xen_callback_t;
 #define PSR_MODE_SYS 0x1f
 
 /* 64 bit modes */
-#ifdef CONFIG_ARM_64
+#ifdef __aarch64__
 #define PSR_MODE_BIT  0x10 /* Set iff AArch32 */
 #define PSR_MODE_EL3h 0x0d
 #define PSR_MODE_EL3t 0x0c