diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index c579661..4934b3e 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -40,7 +40,7 @@
 #include "mbedtls/ecdsa.h"
 #endif
 
-#if defined(MBEDTLS_USE_PSA_CRYPTO)
+#if defined(MBEDTLS_USE_PSA_CRYPTO) || defined(MBEDTLS_PSA_CRYPTO_C)
 #include "psa/crypto.h"
 #endif
 
@@ -234,10 +234,17 @@
 
 /**
  * \brief           Public key container
+ *
+ * \note            The opaque_id is guarded by MBEDTLS_PSA_CRYPTO_C and not
+ *                  only by MBEDTLS_USE_PSA_CRYPTO because it can be used also
+ *                  in mbedtls_pk_sign_ext for RSA keys.
  */
 typedef struct mbedtls_pk_context {
     const mbedtls_pk_info_t *MBEDTLS_PRIVATE(pk_info);    /**< Public key information         */
     void *MBEDTLS_PRIVATE(pk_ctx);                        /**< Underlying public key context  */
+#if defined(MBEDTLS_PSA_CRYPTO_C)
+    mbedtls_svc_key_id_t MBEDTLS_PRIVATE(opaque_id);      /**< Key ID for opaque keys */
+#endif /* MBEDTLS_PSA_CRYPTO_C */
 } mbedtls_pk_context;
 
 #if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)