diff --git a/source/exec.tex b/source/exec.tex
index 26a42d6707..4e5d3fb28d 100644
--- a/source/exec.tex
+++ b/source/exec.tex
@@ -2603,6 +2603,7 @@
 \end{codeblock}
 
 \pnum
+\indexlibraryglobal{tag_of_t}%
 Let \tcode{sndr} be an expression
 such that \tcode{decltype((sndr))} is \tcode{Sndr}.
 The type \tcode{tag_of_t<Sndr>} is as follows: