diff --git a/tree/ntuple/inc/ROOT/RNTupleJoinTable.hxx b/tree/ntuple/inc/ROOT/RNTupleJoinTable.hxx
index 7576451a50def..edb1e1b6c9070 100644
--- a/tree/ntuple/inc/ROOT/RNTupleJoinTable.hxx
+++ b/tree/ntuple/inc/ROOT/RNTupleJoinTable.hxx
@@ -118,11 +118,19 @@ private:
 
          inline std::size_t mix(std::size_t init) const
          {
+#ifdef R__B64
             init ^= init >> 32;
             init *= 0xe9846af9b1a615d;
             init ^= init >> 32;
             init *= 0xe9846af9b1a615d;
             init ^= init >> 28;
+#else
+            init ^= init >> 16;
+            init *= 0x21f0aaad;
+            init ^= init >> 15;
+            init *= 0x735a2d97;
+            init ^= init >> 15;
+#endif
             return init;
          }
       };