diff --git a/polytope_feature/datacube/transformations/datacube_cyclic/datacube_cyclic.py b/polytope_feature/datacube/transformations/datacube_cyclic/datacube_cyclic.py
index b7e402eae..3373dd082 100644
--- a/polytope_feature/datacube/transformations/datacube_cyclic/datacube_cyclic.py
+++ b/polytope_feature/datacube/transformations/datacube_cyclic/datacube_cyclic.py
@@ -1,7 +1,7 @@
 import math
 from copy import deepcopy
 
-from ....utility.combinatorics import unique
+from ....utility.list_tools import unique
 from ..datacube_transformations import DatacubeAxisTransformation
 
 
diff --git a/polytope_feature/engine/hullslicer.py b/polytope_feature/engine/hullslicer.py
index 8d3df84a2..9a99682a6 100644
--- a/polytope_feature/engine/hullslicer.py
+++ b/polytope_feature/engine/hullslicer.py
@@ -9,9 +9,10 @@
 from ..datacube.datacube_axis import UnsliceableDatacubeAxis
 from ..datacube.tensor_index_tree import TensorIndexTree
 from ..shapes import ConvexPolytope
-from ..utility.combinatorics import argmax, argmin, group, tensor_product, unique
+from ..utility.combinatorics import group, tensor_product
 from ..utility.exceptions import UnsliceableShapeError
 from ..utility.geometry import lerp
+from ..utility.list_tools import argmax, argmin, unique
 from .engine import Engine
 
 
diff --git a/polytope_feature/shapes.py b/polytope_feature/shapes.py
index 70ad66b33..e05347b4e 100644
--- a/polytope_feature/shapes.py
+++ b/polytope_feature/shapes.py
@@ -5,6 +5,8 @@
 
 import tripy
 
+from .utility.list_tools import unique
+
 """
 Shapes used for the constructive geometry API of Polytope
 """
@@ -60,11 +62,11 @@ def polytope(self):
 
 # This is the only shape which can slice on axes without a discretizer or interpolator
 class Select(Shape):
-    """Matches several discrete value"""
+    """Matches several discrete values"""
 
     def __init__(self, axis, values, method=None):
         self.axis = axis
-        self.values = values
+        self.values = unique(values)
         self.method = method
 
     def axes(self):
diff --git a/polytope_feature/utility/combinatorics.py b/polytope_feature/utility/combinatorics.py
index 629ebbec8..4040c40db 100644
--- a/polytope_feature/utility/combinatorics.py
+++ b/polytope_feature/utility/combinatorics.py
@@ -46,19 +46,3 @@ def validate_axes(actual_axes, test_axes):
         raise AxisNotFoundError(ax)
 
     return True
-
-
-def unique(points):
-    points.sort()
-    points = [k for k, _ in itertools.groupby(points)]
-    return points
-
-
-def argmin(points):
-    amin = min(range(len(points)), key=points.__getitem__)
-    return amin
-
-
-def argmax(points):
-    amax = max(range(len(points)), key=points.__getitem__)
-    return amax
diff --git a/polytope_feature/utility/list_tools.py b/polytope_feature/utility/list_tools.py
index 2d18917c1..51b8c7fec 100644
--- a/polytope_feature/utility/list_tools.py
+++ b/polytope_feature/utility/list_tools.py
@@ -1,3 +1,6 @@
+import itertools
+
+
 def bisect_left_cmp(arr, val, cmp):
     left = -1
     r = len(arr)
@@ -20,3 +23,19 @@ def bisect_right_cmp(arr, val, cmp):
         else:
             r = e
     return r
+
+
+def unique(points):
+    points.sort()
+    points = [k for k, _ in itertools.groupby(points)]
+    return points
+
+
+def argmin(points):
+    amin = min(range(len(points)), key=points.__getitem__)
+    return amin
+
+
+def argmax(points):
+    amax = max(range(len(points)), key=points.__getitem__)
+    return amax
diff --git a/tests/test_slicing_xarray_3D.py b/tests/test_slicing_xarray_3D.py
index 06df3ec6b..72f68d0ff 100644
--- a/tests/test_slicing_xarray_3D.py
+++ b/tests/test_slicing_xarray_3D.py
@@ -249,3 +249,11 @@ def test_intersection_point_disk_polygon(self):
         result = self.API.retrieve(request)
         paths = [r.flatten().values() for r in result.leaves]
         assert ((pd.Timestamp("2000-01-01 00:00:00"),), (3,), (1,)) in paths
+
+    def test_duplicate_values_select(self):
+        request = Request(Select("step", [3, 3]), Select("level", [1]), Select("date", ["2000-01-01"]))
+        result = self.API.retrieve(request)
+        result.pprint()
+        assert len(result.leaves) == 1
+        path = result.leaves[0].flatten()["step"]
+        assert len(path) == 1