diff --git a/include/psa/crypto_values.h b/include/psa/crypto_values.h
index 526b454..9ce8b68 100644
--- a/include/psa/crypto_values.h
+++ b/include/psa/crypto_values.h
@@ -847,6 +847,9 @@
     (PSA_ALG_IS_KEY_DERIVATION(alg) &&              \
      (alg) & PSA_ALG_KEY_DERIVATION_STRETCHING_FLAG)
 
+/** An invalid algorithm identifier value. */
+#define PSA_ALG_NONE                            ((psa_algorithm_t)0)
+
 #define PSA_ALG_HASH_MASK                       ((psa_algorithm_t)0x000000ff)
 /** MD5 */
 #define PSA_ALG_MD5                             ((psa_algorithm_t)0x02000003)