diff --git a/km3io/offline.py b/km3io/offline.py
index 9a29e13484a25e6d92a47dd300bafb9c08844390..ee643c69d44554ad2356c21fe5859d9250b081f6 100644
--- a/km3io/offline.py
+++ b/km3io/offline.py
@@ -45,6 +45,7 @@ def fitinf(fitparam, tracks):
         params = fit[count_nested(fit, axis=1) > index]
         return params[:, index]
 
+
 def fitparams():
     """name of the fit parameters as defined in the official
     KM3NeT-Dataformat.
@@ -56,6 +57,7 @@ def fitparams():
     """
     return fitparameters.keys()
 
+
 def count_nested(Array, axis=0):
     """count elements in a nested awkward Array.
 
@@ -80,6 +82,7 @@ def count_nested(Array, axis=0):
     if axis == 2:
         return ak1.count(Array, axis=2)
 
+
 def best_track(tracks, strategy="first", rec_stages=None):
     """best track selection based on different strategies
 
@@ -96,7 +99,6 @@ def best_track(tracks, strategy="first", rec_stages=None):
     #     mask = tracks.rec_stages[]
 
 
-
 EVENTS_MAP = BranchMapper(name="events",
                           key="Evt",
                           extra={
diff --git a/tests/test_offline.py b/tests/test_offline.py
index 994df65cab75f530f5b267e7ba2269b301de0b3b..2f7bb02d87f0f154ffd58aff042c40370b708492 100644
--- a/tests/test_offline.py
+++ b/tests/test_offline.py
@@ -36,6 +36,7 @@ class TestFitinf(unittest.TestCase):
 
         assert "JGANDALF_BETA0_RAD" in keys
 
+
 class TestCountNested(unittest.TestCase):
     def test_count_nested(self):
         fit = OFFLINE_FILE.events.tracks.fitinf