diff --git a/docs/firmware-design.rst b/docs/firmware-design.rst
index 997d29b..6bbf12e 100644
--- a/docs/firmware-design.rst
+++ b/docs/firmware-design.rst
@@ -2425,7 +2425,7 @@
 References
 ----------
 
-.. [#] Trusted Board Boot Requirements CLIENT PDD (ARM DEN 0006B-5). Available
+.. [#] Trusted Board Boot Requirements CLIENT PDD (ARM DEN0006C-1). Available
        under NDA through your ARM account representative.
 .. [#] `Power State Coordination Interface PDD`_
 .. [#] `SMC Calling Convention PDD`_