diff --git a/km3buu/output.py b/km3buu/output.py
index d1119c0abde019a56c4d845cf434333bdf8b0654..9d7b2c401d9a1a3be514b1c7af1fe300aeae72fe 100644
--- a/km3buu/output.py
+++ b/km3buu/output.py
@@ -49,6 +49,7 @@ FLUXDESCR_FILENAME = "neutrino_initialized_energyFlux.dat"
 XSECTION_FILENAMES = {"all": "neutrino_absorption_cross_section_ALL.dat"}
 
 SECONDS_PER_YEAR = 365.25 * 24 * 60 * 60
+SECONDS_WEIGHT_TIMESPAN = 1
 
 PARTICLE_COLUMNS = ["E", "Px", "Py", "Pz", "barcode"]
 EVENTINFO_COLUMNS = [
@@ -341,7 +342,7 @@ class GiBUUOutput:
             energy_factor = energy_phase_space * inv_gen_flux
         else:
             energy_factor = 1
-        env_factor = volume * SECONDS_PER_YEAR
+        env_factor = volume * SECONDS_WEIGHT_TIMESPAN
         retval = env_factor * solid_angle * energy_factor * xsec * 10**-42 * target_density
         return retval
 
@@ -436,6 +437,8 @@ class GiBUUOutput:
         """
         import pandas as pd
         df = ak.to_pandas(self.arrays)
+        if len(df) == 0:
+            return df
         sec_df = df[df.index.get_level_values(1) == 0].copy()
         sec_df.loc[:, "E"] = sec_df.lepOut_E
         sec_df.loc[:, "Px"] = sec_df.lepOut_Px