diff --git a/include/mbedtls/md.h b/include/mbedtls/md.h
index 69f1689..85ecc43 100644
--- a/include/mbedtls/md.h
+++ b/include/mbedtls/md.h
@@ -63,10 +63,16 @@
     MBEDTLS_MD_RIPEMD160, /**< The RIPEMD-160 message digest. */
 } mbedtls_md_type_t;
 
-#if defined(MBEDTLS_SHA512_C) || defined(MBEDTLS_SHA384_C)
+#if defined(MBEDTLS_SHA512_C)
 #define MBEDTLS_MD_MAX_SIZE         64  /* longest known is SHA512 */
+#elif defined(MBEDTLS_SHA384_C)
+#define MBEDTLS_MD_MAX_SIZE         48  /* longest known is SHA384 */
+#elif defined(MBEDTLS_SHA256_C)
+#define MBEDTLS_MD_MAX_SIZE         32  /* longest known is SHA256 */
+#elif defined(MBEDTLS_SHA224_C)
+#define MBEDTLS_MD_MAX_SIZE         28  /* longest known is SHA224 */
 #else
-#define MBEDTLS_MD_MAX_SIZE         32  /* longest known is SHA256 or less */
+#define MBEDTLS_MD_MAX_SIZE         20  /* longest known is SHA1 or RIPE MD-160 */
 #endif
 
 #if defined(MBEDTLS_SHA512_C)