diff --git a/lib/psa/measured_boot_private.h b/lib/psa/measured_boot_private.h
new file mode 100644
index 0000000..649c3f6
--- /dev/null
+++ b/lib/psa/measured_boot_private.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#ifndef PSA_MEASURED_BOOT_PRIVATE_H
+#define PSA_MEASURED_BOOT_PRIVATE_H
+
+#include <stdint.h>
+
+/* Measured boot message types that distinguish its services */
+#define RSS_MEASURED_BOOT_EXTEND	1002U
+
+struct measured_boot_extend_iovec_t {
+	uint8_t  index;
+	uint8_t  lock_measurement;
+	uint32_t measurement_algo;
+	uint8_t  sw_type[SW_TYPE_MAX_SIZE];
+	uint8_t  sw_type_size;
+};
+
+#endif /* PSA_MEASURED_BOOT_PRIVATE_H */