diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
index f40307cb..43715892 100644
--- a/boot/zephyr/Kconfig
+++ b/boot/zephyr/Kconfig
@@ -30,7 +30,6 @@ config BOOT_USE_TINYCRYPT
 	# 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.
-	depends on ! MBEDTLS
 	help
 	  Use TinyCrypt for crypto primitives.
 
@@ -41,7 +40,6 @@ config BOOT_USE_CC310
 	# 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.
-	depends on ! MBEDTLS
 	help
 	  Use cc310 for crypto primitives.
 
diff --git a/boot/zephyr/include/mcuboot_config/mcuboot_config.h b/boot/zephyr/include/mcuboot_config/mcuboot_config.h
index ed62d98e..4719d6d2 100644
--- a/boot/zephyr/include/mcuboot_config/mcuboot_config.h
+++ b/boot/zephyr/include/mcuboot_config/mcuboot_config.h
@@ -34,6 +34,14 @@
 #define MCUBOOT_SIGN_ED25519
 #endif
 
+#if defined(CONFIG_BOOT_USE_TINYCRYPT)
+#  if defined(CONFIG_MBEDTLS) || defined(CONFIG_BOOT_USE_CC310)
+#     error "One crypto library implementation allowed at a time."
+#  endif
+#elif defined(CONFIG_MBEDTLS) && defined(CONFIG_BOOT_USE_CC310)
+#     error "One crypto library implementation allowed at a time."
+#endif
+
 #ifdef CONFIG_BOOT_USE_MBEDTLS
 #define MCUBOOT_USE_MBED_TLS
 #elif defined(CONFIG_BOOT_USE_TINYCRYPT)