diff --git a/include/psa/crypto_types.h b/include/psa/crypto_types.h
index f9811bd..03fe9bc 100644
--- a/include/psa/crypto_types.h
+++ b/include/psa/crypto_types.h
@@ -67,21 +67,29 @@
 
 /** The type of PSA elliptic curve identifiers.
  *
- * The encoding of curve identifiers is aligned with the
+ * The encoding of curve identifiers is taken from the
  * TLS Supported Groups Registry (formerly known as the
  * TLS EC Named Curve Registry)
  * https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-8
  * The values are defined by RFC 8422 and RFC 7027.
+ *
+ * This specification defines identifiers for some of the curves in the IANA
+ * registry. Implementations that support other curves that are in the IANA
+ * registry should use the IANA value and a implementation-specific identifier.
  */
 typedef uint16_t psa_ecc_curve_t;
 
 /** The type of PSA Diffie-Hellman group identifiers.
  *
- * The encoding of group identifiers is aligned with the
+ * The encoding of group identifiers is taken from the
  * TLS Supported Groups Registry (formerly known as the
  * TLS EC Named Curve Registry)
  * https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-8
  * The values are defined by RFC 7919.
+ *
+ * This specification defines identifiers for some of the groups in the IANA
+ * registry. Implementations that support other groups that are in the IANA
+ * registry should use the IANA value and a implementation-specific identifier.
  */
 typedef uint16_t psa_dh_group_t;