--- a/VTK/ThirdParty/libproj/vtklibproj/src/proj_json_streaming_writer.hpp
+++ b/VTK/ThirdParty/libproj/vtklibproj/src/proj_json_streaming_writer.hpp
@@ -33,6 +33,7 @@
 
 #include <vector>
 #include <string>
+#include <cstdint>
 
 #define CPL_DLL