diff --git a/meta-nuvoton/conf/machine/include/npcm8xx.inc b/meta-nuvoton/conf/machine/include/npcm8xx.inc
index e8d5587..d3cb516 100644
--- a/meta-nuvoton/conf/machine/include/npcm8xx.inc
+++ b/meta-nuvoton/conf/machine/include/npcm8xx.inc
@@ -38,6 +38,8 @@
 
 PREFERRED_VERSION_trusted-firmware-a = "2.6.0"
 
+PREFERRED_VERSION_optee-os = "3.18.0"
+
 UBOOT_MKIMAGE:append:npcm8xx = " -E -B 8"
 
 COMPATIBLE_MACHINE:npcm8xx = "npcm8xx"