diff --git a/src/contrib/graphbuilderadapter.h b/src/contrib/graphbuilderadapter.h
index 8e5cc07..4f0b80c 100644
--- a/src/contrib/graphbuilderadapter.h
+++ b/src/contrib/graphbuilderadapter.h
@@ -5,6 +5,7 @@
 #pragma once
 #endif
 
+#include <cstdlib>
 #include <map>
 #include <stack>
 #include "yaml-cpp/eventhandler.h"
diff --git a/src/ptr_stack.h b/src/ptr_stack.h
index 75fc923..4c6af11 100644
--- a/src/ptr_stack.h
+++ b/src/ptr_stack.h
@@ -6,6 +6,7 @@
 #endif
 
 #include "yaml-cpp/noncopyable.h"
+#include <cstdlib>
 #include <memory>
 #include <vector>
 
diff --git a/src/ptr_vector.h b/src/ptr_vector.h
index e798208..aa103b8 100644
--- a/src/ptr_vector.h
+++ b/src/ptr_vector.h
@@ -6,6 +6,7 @@
 #endif
 
 #include "yaml-cpp/noncopyable.h"
+#include <cstdlib>
 #include <memory>
 #include <vector>