diff --git a/IfcPlusPlus/src/external/Carve/src/include/carve/rtree.hpp b/IfcPlusPlus/src/external/Carve/src/include/carve/rtree.hpp
index e5f094591..b928bf4c9 100644
--- a/IfcPlusPlus/src/external/Carve/src/include/carve/rtree.hpp
+++ b/IfcPlusPlus/src/external/Carve/src/include/carve/rtree.hpp
@@ -32,6 +32,7 @@
 #include <iostream>
 
 #include <cmath>
+#include <cstdint>
 #include <limits>
 
 namespace carve {