diff --git a/python/tests/beagle_numba.py b/python/tests/beagle_numba.py
index 3f9111f638..e199d8cfde 100644
--- a/python/tests/beagle_numba.py
+++ b/python/tests/beagle_numba.py
@@ -382,9 +382,11 @@ def interpolate_allele_probs(sm, ref_h, typed_pos, untyped_pos, typed_cm, untype
             for a in alleles:
                 if ref_h[i, j] == a:
                     if k == 0:
+                        assert w == 1.0, "Weight should be 1.0."
                         probs[i, a] += sm[k, j]
                     if k == m:
                         # FIXME: It's unclear how BEAGLE handles this case.
+                        assert w == 0.0, "Weight should be 0.0."
                         probs[i, a] += sm[k - 1, j]
                     else:
                         probs[i, a] += w * sm[k - 1, j]