diff --git a/src/lib.cpp b/src/lib.cpp
index c2fb753..9a3adf3 100644
--- a/src/lib.cpp
+++ b/src/lib.cpp
@@ -1,3 +1,5 @@
+#include <cstdlib>
+
 #include "parser3.h"
 #include "weaseljson.h"