diff --git a/arch/arm/cpu/arm920t/Makefile b/arch/arm/cpu/arm920t/Makefile
index 6582938..1832b9d 100644
--- a/arch/arm/cpu/arm920t/Makefile
+++ b/arch/arm/cpu/arm920t/Makefile
@@ -13,3 +13,9 @@
 obj-$(CONFIG_EP93XX) += ep93xx/
 obj-$(CONFIG_IMX) += imx/
 obj-$(CONFIG_S3C24X0) += s3c24x0/
+
+# some files can only build in ARM mode
+
+ifdef CONFIG_SYS_THUMB_BUILD
+CFLAGS_cpu.o := -marm
+endif