diff --git a/km3buu/output.py b/km3buu/output.py
index 8ab8245506a18ce0a7a1aa2005ee0490e6195296..e089d7736ae4ea9f76f0d67848b679acdf83831b 100644
--- a/km3buu/output.py
+++ b/km3buu/output.py
@@ -301,14 +301,14 @@ class GiBUUOutput:
             
         """
         root_tupledata = self.arrays
-        energy_phase_space = self.flux_interpolation.integral(
-            self._energy_min, self._energy_max)
         xsec = self._event_xsec(
             root_tupledata
         ) * self.A  #xsec_per_nucleon * no_nucleons in the core
         if self.flux_data is not None:
             inv_gen_flux = np.power(
                 self.flux_interpolation(root_tupledata.lepIn_E), -1)
+            energy_phase_space = self.flux_interpolation.integral(
+                self._energy_min, self._energy_max)
             energy_factor = energy_phase_space * inv_gen_flux
         else:
             energy_factor = 1