diff --git a/boot/zephyr/include/mcuboot-mbedtls-cfg.h b/boot/zephyr/include/mcuboot-mbedtls-cfg.h
index 0eb6e74..2bab537 100644
--- a/boot/zephyr/include/mcuboot-mbedtls-cfg.h
+++ b/boot/zephyr/include/mcuboot-mbedtls-cfg.h
@@ -23,7 +23,9 @@
 
 #if defined(CONFIG_BOOT_SIGNATURE_TYPE_RSA) || defined(CONFIG_BOOT_ENCRYPT_RSA)
 #include "config-rsa.h"
-#elif defined(CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256) || defined(CONFIG_BOOT_ENCRYPT_EC256)
+#elif defined(CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256) || \
+      defined(CONFIG_BOOT_ENCRYPT_EC256) || \
+      (defined(CONFIG_BOOT_ENCRYPT_X25519) && !defined(CONFIG_BOOT_SIGNATURE_TYPE_ED25519))
 #include "config-asn1.h"
 #elif defined(CONFIG_BOOT_SIGNATURE_TYPE_ED25519)
 #include "config-ed25519.h"