diff --git a/filter_functions/basis.py b/filter_functions/basis.py
index bf47b49..97f14ea 100644
--- a/filter_functions/basis.py
+++ b/filter_functions/basis.py
@@ -281,7 +281,7 @@ def istraceless(self) -> bool:
         if self._istraceless is None:
             trace = np.einsum('...jj', self)
             trace = util.remove_float_errors(trace, self.d**2)
-            nonzero = trace.nonzero()
+            nonzero = np.atleast_1d(trace).nonzero()
             if nonzero[0].size == 0:
                 self._istraceless = True
             elif nonzero[0].size == 1:
diff --git a/tests/test_basis.py b/tests/test_basis.py
index 5da71c1..edfacb1 100644
--- a/tests/test_basis.py
+++ b/tests/test_basis.py
@@ -28,7 +28,6 @@
 import numpy as np
 import pytest
 from filter_functions import util
-from scipy import stats, linalg
 from sparse import COO
 from tests import testutil
 from tests.testutil import rng