diff --git a/km3buu/output.py b/km3buu/output.py
index 4d741b1c1579048351e61242a7ea2df94b2d24df..cbd51c2c9bdd61ca6ffd529495999bf74a40eda6 100644
--- a/km3buu/output.py
+++ b/km3buu/output.py
@@ -614,7 +614,7 @@ def write_detector_file(gibuu_output,
     bjorkeny = event_data.By
 
     tau_secondaries = None
-    if propagate_tau and abs(nu_type) == 16:
+    if propagate_tau and abs(nu_type) == 16 and ichan == 2:
         from .propagation import propagate_lepton
         tau_secondaries = propagate_lepton(event_data, np.sign(nu_type) * 15)