diff --git a/include/mbedtls/md.h b/include/mbedtls/md.h
index a142903..d72b7fc 100644
--- a/include/mbedtls/md.h
+++ b/include/mbedtls/md.h
@@ -112,6 +112,9 @@
 #define MBEDTLS_MD_CAN_SHA512
 #define MBEDTLS_MD_SOME_LEGACY
 #endif
+#if defined(MBEDTLS_SHA3_C)
+#define MBEDTLS_MD_CAN_SHA3
+#endif
 #if defined(MBEDTLS_RIPEMD160_C)
 #define MBEDTLS_MD_CAN_RIPEMD160
 #define MBEDTLS_MD_SOME_LEGACY
@@ -155,6 +158,16 @@
     MBEDTLS_MD_SHA3_512,    /**< The SHA3-512 message digest. */
 } mbedtls_md_type_t;
 
+/* Note: this should always be >= PSA_HASH_MAX_SIZE
+ * in all builds with both CRYPTO_C and MD_LIGHT.
+ *
+ * This is to make things easier for modules such as TLS that may define a
+ * buffer size using MD_MAX_SIZE in a part of the code that's common to PSA
+ * and legacy, then assume the buffer's size is PSA_HASH_MAX_SIZE in another
+ * part of the code based on PSA.
+ *
+ * Currently both macros have the same value, avoiding such issues.
+ */
 #if defined(MBEDTLS_MD_CAN_SHA512) || defined(MBEDTLS_SHA3_C)
 #define MBEDTLS_MD_MAX_SIZE         64  /* longest known is SHA512 */
 #elif defined(MBEDTLS_MD_CAN_SHA384)
@@ -168,7 +181,7 @@
                                            or smaller (MD5 and earlier) */
 #endif
 
-#if defined(MBEDTLS_SHA3_C)
+#if defined(MBEDTLS_MD_CAN_SHA3)
 #define MBEDTLS_MD_MAX_BLOCK_SIZE         144 /* the longest known is SHA3-224 */
 #elif defined(MBEDTLS_MD_CAN_SHA512)
 #define MBEDTLS_MD_MAX_BLOCK_SIZE         128
@@ -317,6 +330,20 @@
 unsigned char mbedtls_md_get_size(const mbedtls_md_info_t *md_info);
 
 /**
+ * \brief           This function gives the message-digest size associated to
+ *                  message-digest type.
+ *
+ * \param md_type   The message-digest type.
+ *
+ * \return          The size of the message-digest output in Bytes,
+ *                  or 0 if the message-digest type is not known.
+ */
+static inline unsigned char mbedtls_md_get_size_from_type(mbedtls_md_type_t md_type)
+{
+    return mbedtls_md_get_size(mbedtls_md_info_from_type(md_type));
+}
+
+/**
  * \brief           This function extracts the message-digest type from the
  *                  message-digest information structure.
  *