diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
index 2cfd7b8..baa807c 100644
--- a/boot/zephyr/Kconfig
+++ b/boot/zephyr/Kconfig
@@ -30,7 +30,7 @@
 	# When building for ECDSA, we use our own copy of mbedTLS, so the
 	# Zephyr one must not be enabled or the MBEDTLS_CONFIG_FILE macros
 	# will collide.
-	select MBEDTLS_PROMPTLESS
+	select MBEDTLS_PROMPTLESS if ZEPHYR_MBEDTLS_MODULE
 	help
 	  Use TinyCrypt for crypto primitives.