diff --git a/python/sage_helper.py b/python/sage_helper.py
index 4881c67b..95aa7854 100644
--- a/python/sage_helper.py
+++ b/python/sage_helper.py
@@ -37,10 +37,11 @@ def sage_method(function):
         from sage.all import VectorSpace, ChainComplex
         from sage.all import ComplexBallField, exp, sin, block_matrix, prime_range, det
         from sage.all import LaurentPolynomialRing, AbelianGroup, GroupAlgebra
+        from sage.all import is_prime
     except ImportError:
         # Modularized Sage library
         from sage.algebras.group_algebra import GroupAlgebra
-        from sage.arith.misc import gcd, xgcd
+        from sage.arith.misc import gcd, xgcd, is_prime
         from sage.combinat.subset import powerset
         from sage.functions.hyperbolic import arccosh
         from sage.functions.log import exp
diff --git a/python/snap/slice_obs_HKL.py b/python/snap/slice_obs_HKL.py
index 884f989a..752e2230 100644
--- a/python/snap/slice_obs_HKL.py
+++ b/python/snap/slice_obs_HKL.py
@@ -45,7 +45,7 @@
 
 from ..sage_helper import _within_sage, sage_method
 if _within_sage:
-    from ..sage_helper import ZZ, PolynomialRing, vector, matrix, identity_matrix, MatrixSpace, block_matrix, prime_range
+    from ..sage_helper import ZZ, PolynomialRing, vector, matrix, identity_matrix, MatrixSpace, block_matrix, prime_range, is_prime
     from ..sage_helper import LaurentPolynomialRing, GF, CyclotomicField, ChainComplex
 
     from .nsagetools import (MapToFreeAbelianization, compute_torsion,