diff --git a/sammy/src/io/CoverxIO.cpp b/sammy/src/io/CoverxIO.cpp
index eb3bf9ad74c67e51b1b362e3be7c8f4cf7ae665a..633872c8acf8a6c705e2c8fb6eff884820b34231 100644
--- a/sammy/src/io/CoverxIO.cpp
+++ b/sammy/src/io/CoverxIO.cpp
@@ -132,10 +132,11 @@ namespace sammy{
         }
 
         CovToolBox tools;
-        endfendf::File33 f33;
         std::ofstream outFile("sammy.f33");
+        endf::EndfWriterInterface writer(outFile,za,awr);
         tools.fillCrossCovFromCoverx(covFile,ccList);
-        f33.writeData(outFile,ccList,za,awr);
+        writer.setType("endf"); // makes it file 33 rather than GNDS
+        writer.writeCrossCovariance(ccList);
     }
 }
 
diff --git a/sammy/src/io/CoverxIO.h b/sammy/src/io/CoverxIO.h
index bfc2ff9ef9dc2eb6fe7c2be665016c0f55c0ddd0..697ea84f1b9a857c601a6e474759d4e7cbc8605f 100644
--- a/sammy/src/io/CoverxIO.h
+++ b/sammy/src/io/CoverxIO.h
@@ -11,7 +11,7 @@
 #include "ScaleData/Core/io/CoverxReader.h"
 #include "ScaleUtils/EndfLib/CovarianceContainer.h"
 #include "../salmon/CovToolBox.h"
-#include "ScaleUtils/EndfLib/endf/File33.h"
+#include "ScaleUtils/EndfLib/EndfWriterInterface.h"
 #include "../salmon/GridData.h"
 #include "../endf/CovarianceData.h"