diff --git a/lisainstrument/regular_interpolators.py b/lisainstrument/regular_interpolators.py
index 6a99c1cd75ae40ce79ba8ea98fb346d5105819c2..fb7a248c849a3f2545ec7384f470e5a5fe016f10 100644
--- a/lisainstrument/regular_interpolators.py
+++ b/lisainstrument/regular_interpolators.py
@@ -155,6 +155,7 @@ class RegularInterpLagrange(RegularInterpCore):
     """
 
     @staticmethod
+    @functools.cache
     def _make_firs(length: int, offset: int) -> list[FilterFirNumpyType]:
         """Set up lagrange polynomials and convert coefficients to FIR filters"""
         plag = make_lagrange_polynomials(length, offset)