diff --git a/tmva/tmva/inc/TMVA/RTensor.hxx b/tmva/tmva/inc/TMVA/RTensor.hxx
index ad152f219a98c..795cc7068966b 100644
--- a/tmva/tmva/inc/TMVA/RTensor.hxx
+++ b/tmva/tmva/inc/TMVA/RTensor.hxx
@@ -3,6 +3,7 @@
 
 #include <vector>
 #include <cstddef>     // std::size_t
+#include <cstdint>
 #include <stdexcept>   // std::runtime_error
 #include <sstream>     // std::stringstream
 #include <memory>      // std::shared_ptr