diff --git a/example/constexpr_float_arithmetic_examples.cpp b/example/constexpr_float_arithmetic_examples.cpp
index 8d7a2d9a..912e62ed 100644
--- a/example/constexpr_float_arithmetic_examples.cpp
+++ b/example/constexpr_float_arithmetic_examples.cpp
@@ -7,6 +7,7 @@
 // section Literal Types and constexpr Support.
 
 #include <iostream>
+#include <boost/config.hpp>
 
 #ifdef BOOST_HAS_FLOAT128
 #include <boost/multiprecision/float128.hpp>