diff --git a/sim/Cargo.toml b/sim/Cargo.toml
index ac3edba..ddf3b88 100644
--- a/sim/Cargo.toml
+++ b/sim/Cargo.toml
@@ -10,6 +10,7 @@
 sig-rsa = ["mcuboot-sys/sig-rsa"]
 sig-rsa3072 = ["mcuboot-sys/sig-rsa3072"]
 sig-ecdsa = ["mcuboot-sys/sig-ecdsa"]
+sig-ecdsa-mbedtls = ["mcuboot-sys/sig-ecdsa-mbedtls"]
 sig-ed25519 = ["mcuboot-sys/sig-ed25519"]
 overwrite-only = ["mcuboot-sys/overwrite-only"]
 swap-move = ["mcuboot-sys/swap-move"]
diff --git a/sim/mcuboot-sys/Cargo.toml b/sim/mcuboot-sys/Cargo.toml
index 829d2ec..19114f9 100644
--- a/sim/mcuboot-sys/Cargo.toml
+++ b/sim/mcuboot-sys/Cargo.toml
@@ -21,6 +21,9 @@
 # Verify ECDSA (secp256r1) signatures.
 sig-ecdsa = []
 
+# Verify ECDSA (secp256r1) signatures using mbed TLS
+sig-ecdsa-mbedtls = []
+
 # Verify ED25519 signatures.
 sig-ed25519 = []
 
diff --git a/sim/mcuboot-sys/build.rs b/sim/mcuboot-sys/build.rs
index 36a0dcd..74b19f0 100644
--- a/sim/mcuboot-sys/build.rs
+++ b/sim/mcuboot-sys/build.rs
@@ -12,6 +12,7 @@
     let sig_rsa = env::var("CARGO_FEATURE_SIG_RSA").is_ok();
     let sig_rsa3072 = env::var("CARGO_FEATURE_SIG_RSA3072").is_ok();
     let sig_ecdsa = env::var("CARGO_FEATURE_SIG_ECDSA").is_ok();
+    let sig_ecdsa_mbedtls = env::var("CARGO_FEATURE_SIG_ECDSA_MBEDTLS").is_ok();
     let sig_ed25519 = env::var("CARGO_FEATURE_SIG_ED25519").is_ok();
     let overwrite_only = env::var("CARGO_FEATURE_OVERWRITE_ONLY").is_ok();
     let swap_move = env::var("CARGO_FEATURE_SWAP_MOVE").is_ok();
@@ -97,6 +98,21 @@
 
         conf.file("../../ext/mbedtls-asn1/src/platform_util.c");
         conf.file("../../ext/mbedtls-asn1/src/asn1parse.c");
+    } else if sig_ecdsa_mbedtls {
+        conf.define("MCUBOOT_SIGN_EC256", None);
+        conf.define("MCUBOOT_USE_MBED_TLS", None);
+
+        conf.include("../../ext/mbedtls/crypto/include");
+        conf.file("../../ext/mbedtls/crypto/library/sha256.c");
+        conf.file("csupport/keys.c");
+
+        conf.file("../../ext/mbedtls/crypto/library/asn1parse.c");
+        conf.file("../../ext/mbedtls/crypto/library/bignum.c");
+        conf.file("../../ext/mbedtls/crypto/library/ecdsa.c");
+        conf.file("../../ext/mbedtls/crypto/library/ecp.c");
+        conf.file("../../ext/mbedtls/crypto/library/ecp_curves.c");
+        conf.file("../../ext/mbedtls/crypto/library/platform.c");
+        conf.file("../../ext/mbedtls/crypto/library/platform_util.c");
     } else if sig_ed25519 {
         conf.define("MCUBOOT_SIGN_ED25519", None);
         conf.define("MCUBOOT_USE_TINYCRYPT", None);
@@ -247,6 +263,8 @@
         conf.define("MBEDTLS_CONFIG_FILE", Some("<config-rsa-kw.h>"));
     } else if sig_rsa || sig_rsa3072 || enc_rsa {
         conf.define("MBEDTLS_CONFIG_FILE", Some("<config-rsa.h>"));
+    } else if sig_ecdsa_mbedtls {
+        conf.define("MBEDTLS_CONFIG_FILE", Some("<config-ecdsa.h>"));
     } else if (sig_ecdsa || enc_ec256) && !enc_kw {
         conf.define("MBEDTLS_CONFIG_FILE", Some("<config-asn1.h>"));
     } else if sig_ed25519 || enc_x25519 {
@@ -258,7 +276,7 @@
     conf.file("../../boot/bootutil/src/image_validate.c");
     if sig_rsa || sig_rsa3072 {
         conf.file("../../boot/bootutil/src/image_rsa.c");
-    } else if sig_ecdsa {
+    } else if sig_ecdsa || sig_ecdsa_mbedtls {
         conf.file("../../boot/bootutil/src/image_ec256.c");
     } else if sig_ed25519 {
         conf.file("../../boot/bootutil/src/image_ed25519.c");
diff --git a/sim/mcuboot-sys/csupport/run.c b/sim/mcuboot-sys/csupport/run.c
index 03947fa..0133262 100644
--- a/sim/mcuboot-sys/csupport/run.c
+++ b/sim/mcuboot-sys/csupport/run.c
@@ -230,7 +230,8 @@
     struct boot_rsp rsp;
     struct boot_loader_state *state;
 
-#if defined(MCUBOOT_SIGN_RSA)
+#if defined(MCUBOOT_SIGN_RSA) || \
+    (defined(MCUBOOT_SIGN_EC256) && defined(MCUBOOT_USE_MBED_TLS))
     mbedtls_platform_set_calloc_free(calloc, free);
 #endif