diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index e6abf24..664fc68 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -740,11 +740,40 @@
  *
  * \note  This option only works with the default software implementation of
  *        elliptic curve functionality. It is incompatible with
- *        MBEDTLS_ECP_ALT, MBEDTLS_ECDH_XXX_ALT and MBEDTLS_ECDSA_XXX_ALT.
+ *        MBEDTLS_ECP_ALT, MBEDTLS_ECDH_XXX_ALT, MBEDTLS_ECDSA_XXX_ALT
+ *        and MBEDTLS_ECDH_LEGACY_CONTEXT.
  */
 //#define MBEDTLS_ECP_RESTARTABLE
 
 /**
+ * \def MBEDTLS_ECDH_LEGACY_CONTEXT
+ *
+ * Use a backward compatible ECDH context.
+ *
+ * Mbed TLS supports two formats for ECDH contexts (#mbedtls_ecdh_context
+ * defined in `ecdh.h`). For most applications, the choice of format makes
+ * no difference, since all library functions can work with either format,
+ * except that the new format is incompatible with MBEDTLS_ECP_RESTARTABLE.
+
+ * The new format used when this option is disabled is smaller
+ * (56 bytes on a 32-bit platform). In future versions of the library, it
+ * will support alternative implementations of ECDH operations.
+ * The new format is incompatible with applications that access
+ * context fields directly and with restartable ECP operations.
+ *
+ * Define this macro if you enable MBEDTLS_ECP_RESTARTABLE or if you
+ * want to access ECDH context fields directly. Otherwise you should
+ * comment out this macro definition.
+ *
+ * This option has no effect if #MBEDTLS_ECDH_C is not enabled.
+ *
+ * \note This configuration option is experimental. Future versions of the
+ *       library may modify the way the ECDH context layout is configured
+ *       and may modify the layout of the new context type.
+ */
+#define MBEDTLS_ECDH_LEGACY_CONTEXT
+
+/**
  * \def MBEDTLS_ECDSA_DETERMINISTIC
  *
  * Enable deterministic ECDSA (RFC 6979).