diff --git a/source/utilities.tex b/source/utilities.tex
index 154e787edb..b603afcc3a 100644
--- a/source/utilities.tex
+++ b/source/utilities.tex
@@ -16981,6 +16981,7 @@
 \begin{example}
 \begin{codeblock}
 #include <format>
+#include <string>
 
 enum color { red, green, blue };
 const char* color_names[] = { "red", "green", "blue" };