diff --git a/rules.tex b/rules.tex
index 2b539747fd7c1f84b89668320739fbffe9894f03..71160c949e08889d72bfd756e97128aaa202eb00 100644
--- a/rules.tex
+++ b/rules.tex
@@ -217,6 +217,7 @@ The smell of roasted meat is coming from human flesh roasting over each fire in
 }{}
 
 \subsection{Margins}\index{Margins}
+\index{Failure Margin}
 \label{margin}
 
 Most actions are either a success or a failure, but sometimes the \gls{gm} will request to know a roll's Margin -- i.e. just how well the character has succeeded at the task. The Margin is the number of points over the \gls{tn} a roll has gathered. If the \gls{tn} is 9 and a player scores 11 then the Margin is 2.