diff --git a/include/psa/crypto_values.h b/include/psa/crypto_values.h
index b30f955..524e2dc 100644
--- a/include/psa/crypto_values.h
+++ b/include/psa/crypto_values.h
@@ -2025,6 +2025,9 @@
 
 #define PSA_KEY_LOCATION_VENDOR_FLAG            ((psa_key_location_t)0x800000)
 
+/** The null key identifier.
+ */
+#define PSA_KEY_ID_NULL                         ((psa_key_id_t)0)
 /** The minimum value for a key identifier chosen by the application.
  */
 #define PSA_KEY_ID_USER_MIN                     ((psa_key_id_t)0x00000001)