diff --git a/src/ripple/json/ripple_json.cpp b/src/ripple/json/ripple_json.cpp
index 78c51b18c..d8557ef11 100644
--- a/src/ripple/json/ripple_json.cpp
+++ b/src/ripple/json/ripple_json.cpp
@@ -20,6 +20,7 @@
 #include "BeastConfig.h"
 
 #include <cassert>
+#include <cstdlib>
 #include <iomanip>
 #include <sstream>
 #include <string>