diff --git a/include/mbedtls/sha256.h b/include/mbedtls/sha256.h
index 3d3e3fc..d256352 100644
--- a/include/mbedtls/sha256.h
+++ b/include/mbedtls/sha256.h
@@ -96,6 +96,10 @@
  * \param is224    This determines which function to use. This must be
  *                 either \c 0 for SHA-256, or \c 1 for SHA-224.
  *
+ * \note           is224 must be defined accordingly to the enabled
+ *                 MBEDTLS_SHA224_C/MBEDTLS_SHA256_C symbols otherwise the
+ *                 function will return #MBEDTLS_ERR_SHA512_BAD_INPUT_DATA.
+ *
  * \return         \c 0 on success.
  * \return         A negative error code on failure.
  */