diff --git a/src/error_code.cpp b/src/error_code.cpp
index 155e0e0..b28f49a 100644
--- a/src/error_code.cpp
+++ b/src/error_code.cpp
@@ -27,6 +27,7 @@
 #include <boost/cerrno.hpp>
 #include <vector>
 #include <cstdlib>
+#include <cassert>
 
 using namespace boost::system;