diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index c00875bd0..6dec490c8 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -4584,6 +4584,7 @@ psa_status_t psa_aead_encrypt( mbedtls_svc_key_id_t key,
     else
 #endif /* MBEDTLS_CHACHAPOLY_C */
     {
+        (void) tag;
         return( PSA_ERROR_NOT_SUPPORTED );
     }