diff --git a/common/dataStructures/TapeFile.hpp b/common/dataStructures/TapeFile.hpp
index 29b4ac856363eadbf8dcdbe7c0083feb6f3c841c..a37771ea6645000bc291e6d4c3b8040737655c7e 100644
--- a/common/dataStructures/TapeFile.hpp
+++ b/common/dataStructures/TapeFile.hpp
@@ -64,7 +64,7 @@ struct TapeFile {
    * The copy number of the file. Copy numbers start from 1. Copy number 0 
    * is an invalid copy number. 
    */
-  uint64_t copyNb;
+  uint16_t copyNb;
   /**
    * The time the file recorded in the catalogue. 
    */