diff --git a/sim/mcuboot-sys/build.rs b/sim/mcuboot-sys/build.rs
index 3bf4409..66bba79 100644
--- a/sim/mcuboot-sys/build.rs
+++ b/sim/mcuboot-sys/build.rs
@@ -97,16 +97,18 @@
         conf.file("../../ext/mbedtls-asn1/src/asn1parse.c");
     } else if sig_ed25519 {
         conf.define("MCUBOOT_SIGN_ED25519", None);
-        conf.define("MCUBOOT_USE_MBED_TLS", None);
+        conf.define("MCUBOOT_USE_TINYCRYPT", None);
 
-        conf.include("../../ext/mbedtls/include");
-        conf.file("../../ext/mbedtls/library/sha256.c");
-        conf.file("../../ext/mbedtls/library/sha512.c");
+        conf.include("../../ext/tinycrypt/lib/include");
+        conf.include("../../ext/tinycrypt-sha512/lib/include");
+        conf.include("../../ext/mbedtls-asn1/include");
+        conf.file("../../ext/tinycrypt/lib/source/sha256.c");
+        conf.file("../../ext/tinycrypt-sha512/lib/source/sha512.c");
+        conf.file("../../ext/tinycrypt/lib/source/utils.c");
         conf.file("csupport/keys.c");
         conf.file("../../ext/fiat/src/curve25519.c");
-        conf.file("../../ext/mbedtls/library/platform.c");
-        conf.file("../../ext/mbedtls/library/platform_util.c");
-        conf.file("../../ext/mbedtls/library/asn1parse.c");
+        conf.file("../../ext/mbedtls-asn1/src/platform_util.c");
+        conf.file("../../ext/mbedtls-asn1/src/asn1parse.c");
     } else if !enc_ec256 {
         // No signature type, only sha256 validation. The default
         // configuration file bundled with mbedTLS is sufficient.
@@ -221,7 +223,7 @@
     } else if (sig_ecdsa || enc_ec256) && !enc_kw {
         conf.define("MBEDTLS_CONFIG_FILE", Some("<config-asn1.h>"));
     } else if sig_ed25519 {
-        conf.define("MBEDTLS_CONFIG_FILE", Some("<config-ed25519.h>"));
+        conf.define("MBEDTLS_CONFIG_FILE", Some("<config-asn1.h>"));
     } else if enc_kw {
         conf.define("MBEDTLS_CONFIG_FILE", Some("<config-kw.h>"));
     }