diff --git a/docs/index.rst b/docs/index.rst
index f73ad84..fae38ab 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -46,6 +46,7 @@
    + :doc:`specs/signed-interest`
    + :doc:`specs/certificate-format`
    + :doc:`specs/safe-bag`
+   + :doc:`specs/validation-error-code`
 
 - :doc:`manpages`