diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 0ef73df..01ddb52 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -3365,7 +3365,7 @@
 {
     psa_algorithm_t hash_alg = PSA_ALG_HKDF_GET_HASH( alg );
     uint8_t hash_length = PSA_HASH_LENGTH( hash_alg );
-    psa_hmac_internal_data backup = MBEDTLS_PSA_HMAC_OPERATION_INIT;
+    psa_hmac_internal_data_t backup = MBEDTLS_PSA_HMAC_OPERATION_INIT;
     psa_status_t status, cleanup_status;
 
     /* We can't be wanting more output after block 0xff, otherwise