diff --git a/library/psa_crypto_slot_management.c b/library/psa_crypto_slot_management.c
index f7b7fbe..b2a3c7e 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -542,7 +542,7 @@
 
     *handle = key;
 
-    return psa_unregister_read(slot);
+    return psa_unregister_read_under_mutex(slot);
 
 #else /* MBEDTLS_PSA_CRYPTO_STORAGE_C || MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS */
     (void) key;