diff --git a/include/boost/charconv/to_chars.hpp b/include/boost/charconv/to_chars.hpp
index f5b136b..7e9ca2a 100644
--- a/include/boost/charconv/to_chars.hpp
+++ b/include/boost/charconv/to_chars.hpp
@@ -11,6 +11,7 @@
 #include <array>
 #include <cstring>
 #include <cstdio>
+#include <cerrno>
 
 namespace boost { namespace charconv {