diff --git a/src/error_code.cpp b/src/error_code.cpp
index b9880c0..45099eb 100644
--- a/src/error_code.cpp
+++ b/src/error_code.cpp
@@ -26,6 +26,7 @@
 #include <boost/system/error_code.hpp>
 #include <boost/cerrno.hpp>
 #include <vector>
+#include <cstdlib>
 
 using namespace boost::system;