diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index e96a797..d7662ef 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -1141,7 +1141,10 @@
  *
  * Enable support for PKCS#1 v2.1 encoding.
  *
- * Requires: MBEDTLS_MD_C, MBEDTLS_RSA_C
+ * Requires: MBEDTLS_RSA_C and (MBEDTLS_MD_C or MBEDTLS_PSA_CRYPTO_C).
+ *
+ * \warning If building without MBEDTLS_MD_C, you must call psa_crypto_init()
+ * before doing any PKCS#1 v2.1 operation.
  *
  * This enables support for RSAES-OAEP and RSASSA-PSS operations.
  */