diff --git a/python/tests/beagle.py b/python/tests/beagle.py
index e742a5ebaf..6b28161946 100644
--- a/python/tests/beagle.py
+++ b/python/tests/beagle.py
@@ -426,9 +426,7 @@ def compute_state_probability_matrix(fm, bm):
     return sm
 
 
-def interpolate_allele_probabilities(
-    sm, ref_h, alleles, genotyped_pos, ungenotyped_pos
-):
+def interpolate_allele_probabilities(sm, ref_h, genotyped_pos, ungenotyped_pos):
     """
     Compute the interpolated allele probabilities at ungenotyped markers of
     a query haplotype following Equation 1 of BB2016.
@@ -444,19 +442,16 @@ def interpolate_allele_probabilities(
 
     :param numpy.ndarray sm: HMM state probability matrix at genotyped markers.
     :param numpy.ndarray ref_h: Reference haplotypes subsetted to ungenotyped markers.
-    :param numpy.ndarray alleles: Alleles (ancestral/derived or ACGT encoding).
     :param numpy.ndarray genotyped_pos: Site positions at genotyped markers.
     :param numpy.ndarray ungenotyped_pos: Site positions at ungenotyped markers.
     :return: Interpolated allele probabilities.
     :rtype: numpy.ndarray
     """
+    alleles = np.arange(4)  # ACGT encoding
     assert not np.any(sm < 0), "HMM state probability matrix has negative values."
     assert not np.any(np.isnan(sm)), "HMM state probability matrix has NaN values."
     m = sm.shape[0] - 1
     h = sm.shape[1]
-    assert np.all(
-        np.isin(ref_h, alleles)
-    ), f"Reference haplotypes have alleles absent in {alleles}."
     assert m == len(genotyped_pos)
     x = len(ungenotyped_pos)
     assert (x, h) == ref_h.shape
@@ -600,7 +595,7 @@ def run_beagle(ref_h, query_h, pos, miscall_rate=0.0001, ne=1e6, debug=False):
     # Interpolate allele probabilities at ungenotyped markers.
     alleles = np.arange(4)  # ACGT
     i_allele_probs = interpolate_allele_probabilities(
-        sm, ref_h_ungenotyped, alleles, genotyped_pos, ungenotyped_pos
+        sm, ref_h_ungenotyped, genotyped_pos, ungenotyped_pos
     )
     if debug:
         print("Interpolated allele probabilities")
diff --git a/python/tests/beagle_numba.py b/python/tests/beagle_numba.py
index bff4dcfcaa..df4d68ddb6 100644
--- a/python/tests/beagle_numba.py
+++ b/python/tests/beagle_numba.py
@@ -217,9 +217,7 @@ def compute_state_probability_matrix(fm, bm):
 
 
 @njit
-def interpolate_allele_probabilities(
-    sm, ref_h, alleles, genotyped_pos, ungenotyped_pos
-):
+def interpolate_allele_probabilities(sm, ref_h, genotyped_pos, ungenotyped_pos):
     """
     Compute the interpolated allele probabilities at ungenotyped markers of
     a query haplotype following Equation 1 of BB2016.
@@ -235,12 +233,12 @@ def interpolate_allele_probabilities(
 
     :param numpy.ndarray sm: HMM state probability matrix at genotyped markers.
     :param numpy.ndarray ref_h: Reference haplotypes subsetted to imputed markers.
-    :param numpy.ndarray alleles: Alleles (ancestral/derived or ACGT encoding).
     :param numpy.ndarray genotyped_pos: Site positions at genotyped markers.
     :param numpy.ndarray ungenotyped_pos: Site positions at ungenotyped markers.
     :return: Interpolated allele probabilities.
     :rtype: numpy.ndarray
     """
+    alleles = np.arange(4)  # ACGT encoding
     x = len(ungenotyped_pos)
     weights, marker_interval_start = get_weights(genotyped_pos, ungenotyped_pos)
     p = np.zeros((x, len(alleles)), dtype=np.float64)
@@ -297,7 +295,6 @@ def run_beagle(ref_h, query_h, pos, miscall_rate=0.0001, ne=1e6):
     :return: Imputed alleles and their associated probabilities.
     :rtype: tuple(numpy.ndarray, numpy.ndarray)
     """
-    alleles = np.arange(4)  # ACGT encoding
     # Indices of markers.
     genotyped_pos_idx = np.where(query_h != -1)[0]
     ungenotyped_pos_idx = np.where(query_h == -1)[0]
@@ -321,7 +318,7 @@ def run_beagle(ref_h, query_h, pos, miscall_rate=0.0001, ne=1e6):
     ref_h_ungenotyped = ref_h[ungenotyped_pos_idx, :]
     # Interpolate allele probabilities at ungenotyped markers.
     i_allele_probs = interpolate_allele_probabilities(
-        sm, ref_h_ungenotyped, alleles, genotyped_pos, ungenotyped_pos
+        sm, ref_h_ungenotyped, genotyped_pos, ungenotyped_pos
     )
     # Get MAP alleles at ungenotyped markers.
     imputed_alleles, max_allele_probs = get_map_alleles(i_allele_probs)
@@ -329,7 +326,6 @@ def run_beagle(ref_h, query_h, pos, miscall_rate=0.0001, ne=1e6):
 
 
 def run_tsimpute(ref_ts, query_h, pos):
-    alleles = np.arange(4)  # ACGT encoding
     # Prepare marker positions.
     genotyped_site_ids = np.where(query_h != -1)[0]
     genotyped_pos = pos[genotyped_site_ids]
@@ -354,7 +350,7 @@ def run_tsimpute(ref_ts, query_h, pos):
     sm = compute_state_probability_matrix(fm.decode(), bm.decode())
     # Interpolate allele probabilities.
     allele_probs = interpolate_allele_probabilities(
-        sm, ref_h_x, alleles, genotyped_pos, imputed_pos
+        sm, ref_h_x, genotyped_pos, imputed_pos
     )
     # Get MAP alleles at imputed markers.
     imputed_alleles, max_allele_probs = get_map_alleles(allele_probs)