diff --git a/invisible_cities/database/test_data/Kr83_nexus_v5_03_00_ACTIVE_7bar_10evts_KDST.h5 b/invisible_cities/database/test_data/Kr83_nexus_v5_03_00_ACTIVE_7bar_10evts_KDST.h5
index ca06c16d6c..293ed8b03a 100644
--- a/invisible_cities/database/test_data/Kr83_nexus_v5_03_00_ACTIVE_7bar_10evts_KDST.h5
+++ b/invisible_cities/database/test_data/Kr83_nexus_v5_03_00_ACTIVE_7bar_10evts_KDST.h5
@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:6c9f536250d066c46740bd980947051073aca34dc81d3ba0945696f2159a16b6
-size 22900
+oid sha256:0edd8cb2336802cfa6a40d4fb71fd07ce10d17d214682f6b8b8bad369b6cb20d
+size 22870
diff --git a/invisible_cities/io/kdst_io_test.py b/invisible_cities/io/kdst_io_test.py
index eb22a56e25..513ac2636e 100644
--- a/invisible_cities/io/kdst_io_test.py
+++ b/invisible_cities/io/kdst_io_test.py
@@ -29,6 +29,16 @@ def dump_df(write, df):
                         getattr(evt, col).append(value)
                     except AttributeError:
                         setattr(evt, col, value)
+
+            evt.nS1 = int(evt.nS1)
+            evt.nS2 = int(evt.nS2)
+            for col in ("Z", "DT"):
+                column = list(getattr(evt, col))
+                setattr(evt, col, [])
+                for i in range(evt.nS2):
+                    s1_data = column[:evt.nS1 ]
+                    column  = column[ evt.nS1:]
+                    getattr(evt, col).append(s1_data)
             write(evt)
 
     with tb.open_file(filename, 'w') as h5out: