diff --git a/source/containers.tex b/source/containers.tex
index 1074f9bd43..70e123d966 100644
--- a/source/containers.tex
+++ b/source/containers.tex
@@ -22489,7 +22489,7 @@
 
 \indexlibrarymember{required_span_size}{layout_right::mapping}%
 \begin{itemdecl}
-index_type required_span_size() const noexcept;
+constexpr index_type required_span_size() const noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}