diff --git a/lisainstrument/instrument.py b/lisainstrument/instrument.py
index 20424c8fbb255a101f4f0b937356e64dd38dab5e..243e98581b3a8b8e0c03024612aca9a135f992ca 100755
--- a/lisainstrument/instrument.py
+++ b/lisainstrument/instrument.py
@@ -706,11 +706,11 @@ class Instrument:
                     order,
                     min_delay_time * self.physics_fs,
                     max_delay_time * self.physics_fs,
-                    ShiftBC.FLAT,
-                    ShiftBC.EXCEPTION,
+                    ShiftBC.ZEROPAD,
+                    ShiftBC.ZEROPAD,
                 )
                 op_fix = make_fixed_shift_lagrange_dask(
-                    ShiftBC.FLAT, ShiftBC.EXCEPTION, order
+                    ShiftBC.ZEROPAD, ShiftBC.ZEROPAD, order
                 )
                 self._delay_dynamic = self.numpyfy_dask_multi(op_dyn)
                 self._delay_const = self.numpyfy_dask_multi(op_fix)
@@ -725,11 +725,11 @@ class Instrument:
                     order,
                     min_delay_time * self.physics_fs,
                     max_delay_time * self.physics_fs,
-                    ShiftBC.FLAT,
-                    ShiftBC.EXCEPTION,
+                    ShiftBC.ZEROPAD,
+                    ShiftBC.ZEROPAD,
                 )
                 op_fix = make_fixed_shift_dsp_dask(
-                    ShiftBC.FLAT, ShiftBC.EXCEPTION, order
+                    ShiftBC.ZEROPAD, ShiftBC.ZEROPAD, order
                 )
                 self._delay_dynamic = self.numpyfy_dask_multi(op_dyn)
                 self._delay_const = self.numpyfy_dask_multi(op_fix)