diff --git a/include/CLI/impl/StringTools_inl.hpp b/include/CLI/impl/StringTools_inl.hpp
index 5a120c39e..bab79a37e 100644
--- a/include/CLI/impl/StringTools_inl.hpp
+++ b/include/CLI/impl/StringTools_inl.hpp
@@ -10,6 +10,7 @@
 #include <CLI/StringTools.hpp>
 
 // [CLI11:public_includes:set]
+#include <cstdint>
 #include <string>
 #include <utility>
 #include <vector>