diff --git a/setup.cfg b/setup.cfg
index e31081a3aeb7b2c31a66e939bb22939eb80d707e..0ac79263df9768b05ddaab59f213065411652475 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -54,7 +54,7 @@ where = src
 all =
 dev =
     black==21.6b0
-    km3net-testdata>=0.2.26
+    km3net-testdata>=0.3.3
     ipykernel
     matplotlib
     memory_profiler
diff --git a/src/km3io/offline.py b/src/km3io/offline.py
index a811ae402ace0b5eb7902a64fcb40e856161108c..08127996af8a51088e2d65bceba90f7945d28fc1 100644
--- a/src/km3io/offline.py
+++ b/src/km3io/offline.py
@@ -83,6 +83,7 @@ class OfflineReader(EventReader):
             "len": "mc_trks.len",
             "status": "mc_trks.status",
             "mother_id": "mc_trks.mother_id",
+            "counter": "mc_trks.counter",
             "pdgid": "mc_trks.type",
             "hit_ids": "mc_trks.hit_ids",
             "usr": "mc_trks.usr",  # TODO: trouble with uproot4
diff --git a/tests/test_offline.py b/tests/test_offline.py
index b4310b4ce73b782b324bc819f1a2d0b409eb5c04..2cdf33c64b5f21c2eaf9f3f9ed4b2234f528af1d 100644
--- a/tests/test_offline.py
+++ b/tests/test_offline.py
@@ -491,6 +491,14 @@ class TestOfflineTracks(unittest.TestCase):
         )
 
 
+class TestMisc(unittest.TestCase):
+    def test_mc_tracks_counter(self):
+        r = OfflineReader(data_path("gseagen/DAT000001.gSeaGen.1.aa.root"))
+        np.testing.assert_allclose(
+            [0, 0, 6, 7, 0, 0, 2, 53, 0, 0, 6, 57, 0], r.mc_tracks.counter[0][:13]
+        )
+
+
 class TestBranchIndexingMagic(unittest.TestCase):
     def setUp(self):
         self.events = OFFLINE_FILE.events