diff --git a/include/lib/extensions/twed.h b/include/lib/extensions/twed.h
new file mode 100644
index 0000000..eac4aa3
--- /dev/null
+++ b/include/lib/extensions/twed.h
@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2020, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef TWED_H
+#define TWED_H
+
+#include <stdint.h>
+
+#define TWED_DISABLED U(0xFFFFFFFF)
+
+uint32_t plat_arm_set_twedel_scr_el3(void);
+
+#endif /* TWEDE_H */