diff --git a/include/psa/crypto_struct.h b/include/psa/crypto_struct.h
index efc30b804..5eb262405 100644
--- a/include/psa/crypto_struct.h
+++ b/include/psa/crypto_struct.h
@@ -140,6 +140,7 @@ struct psa_cipher_operation_s
     uint8_t block_size;
     union
     {
+        unsigned dummy; /* Enable easier initializing of the union. */
         mbedtls_cipher_context_t cipher;
     } ctx;
 };