Rename M255 to Curve25519
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 6f346ce..d2074df 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -421,7 +421,7 @@
 #define MBEDTLS_ECP_DP_BP256R1_ENABLED
 #define MBEDTLS_ECP_DP_BP384R1_ENABLED
 #define MBEDTLS_ECP_DP_BP512R1_ENABLED
-#define MBEDTLS_ECP_DP_M255_ENABLED
+#define MBEDTLS_ECP_DP_CURVE25519_ENABLED
 
 /**
  * \def MBEDTLS_ECP_NIST_OPTIM