diff --git a/include/psa/crypto_struct.h b/include/psa/crypto_struct.h
index 3842eab..2cbdcdf 100644
--- a/include/psa/crypto_struct.h
+++ b/include/psa/crypto_struct.h
@@ -203,11 +203,12 @@
     defined(MBEDTLS_PSA_BUILTIN_ALG_TLS12_PSK_TO_MS)
 typedef enum
 {
-    PSA_TLS12_PRF_STATE_INIT,       /* no input provided */
-    PSA_TLS12_PRF_STATE_SEED_SET,   /* seed has been set */
-    PSA_TLS12_PRF_STATE_KEY_SET,    /* key has been set */
-    PSA_TLS12_PRF_STATE_LABEL_SET,  /* label has been set */
-    PSA_TLS12_PRF_STATE_OUTPUT      /* output has been started */
+    PSA_TLS12_PRF_STATE_INIT,             /* no input provided */
+    PSA_TLS12_PRF_STATE_SEED_SET,         /* seed has been set */
+    PSA_TLS12_PRF_STATE_OTHER_KEY_SET,    /* other key has been set - optional */
+    PSA_TLS12_PRF_STATE_KEY_SET,          /* key has been set */
+    PSA_TLS12_PRF_STATE_LABEL_SET,        /* label has been set */
+    PSA_TLS12_PRF_STATE_OUTPUT            /* output has been started */
 } psa_tls12_prf_key_derivation_state_t;
 
 typedef struct psa_tls12_prf_key_derivation_s