diff --git a/library/pk.c b/library/pk.c
index 71ab60d..d92de69 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -879,7 +879,7 @@
         psa_status_t status;
 
         /* export the private key material in the format PSA wants */
-        ec = mbedtls_pk_ec(*pk);
+        ec = mbedtls_pk_ec_rw(*pk);
         d_len = PSA_BITS_TO_BYTES(ec->grp.nbits);
         if ((ret = mbedtls_ecp_write_key(ec, d, d_len)) != 0) {
             return ret;