diff --git a/devtools/container/build.py b/devtools/container/build.py
index f575a767a..d0af2a7a4 100644
--- a/devtools/container/build.py
+++ b/devtools/container/build.py
@@ -51,8 +51,10 @@
         log.info(f'installing Nutils from {wheel}')
     else:
         log.info(f'building wheel for commit {commit}')
-        run(sys.executable, 'setup.py', 'bdist_wheel', cwd=str(src.path), env=dict(SOURCE_DATE_EPOCH=str(src.get_commit_timestamp('HEAD'))))
-        wheel, = (src.path / 'dist').glob('nutils-*.whl')
+        dist_dir = src.path / 'dist'
+        dist_dir.mkdir()
+        run(sys.executable, '-m', 'pip', 'wheel', '--no-deps', str(src.path), cwd=str(src.path / 'dist'), env=dict(SOURCE_DATE_EPOCH=str(src.get_commit_timestamp('HEAD'))))
+        wheel, = dist_dir.glob('nutils-*.whl')
 
     if args.examples:
         examples = Path(args.examples)
@@ -66,7 +68,7 @@
 
     container = stack.enter_context(Container.new_from(base, mounts=[Mount(src=wheel, dst=f'/{wheel.name}')]))
 
-    container.run('pip', 'install', '--no-cache-dir', f'/{wheel.name}[export_mpl,import_gmsh,matrix_scipy]', env=dict(PYTHONHASHSEED='0'))
+    container.run('pip', 'install', '--break-system-packages', '--no-cache-dir', f'/{wheel.name}[export_mpl,import_gmsh,matrix_scipy]', env=dict(PYTHONHASHSEED='0'))
     container.add_label('org.opencontainers.image.url', 'https://github.com/evalf/nutils')
     container.add_label('org.opencontainers.image.source', 'https://github.com/evalf/nutils')
     container.add_label('org.opencontainers.image.authors', 'Evalf')
diff --git a/devtools/container/build_base.py b/devtools/container/build_base.py
index e1a42a81d..176da2d4b 100644
--- a/devtools/container/build_base.py
+++ b/devtools/container/build_base.py
@@ -14,12 +14,13 @@
 
 log.info(f'building container base image with name `{image_name}`')
 
-with Container.new_from('debian:bullseye', network='host') as container:
-    container.run('sed', '-i', 's/ main$/ main contrib non-free/', '/etc/apt/sources.list')
+with Container.new_from('debian:bookworm', network='host') as container:
+    container.run('sed', '-i', 's/^Components: .*$/Components: main contrib non-free/', '/etc/apt/sources.list.d/debian.sources')
     container.run('apt', 'update')
-    # Package `libtbb2` is required when using Intel MKL with environment
+    # Package `libtbb12` is required when using Intel MKL with environment
     # variable `MKL_THREADING_LAYER` set to `TBB`, which is nowadays the default.
-    container.run('apt', 'install', '-y', '--no-install-recommends', 'python3', 'python3-pip', 'python3-wheel', 'python3-ipython', 'python3-numpy', 'python3-scipy', 'python3-matplotlib', 'python3-pil', 'libmkl-rt', 'libomp-dev', 'libtbb2', 'python3-gmsh', env=dict(DEBIAN_FRONTEND='noninteractive'))
+    container.run('apt', 'install', '-y', '--no-install-recommends', 'python3', 'python3-pip', 'python3-wheel', 'python3-ipython', 'python3-numpy', 'python3-scipy', 'python3-matplotlib', 'python3-pil', 'libmkl-rt', 'libomp-dev', 'libtbb12', 'python3-gmsh', env=dict(DEBIAN_FRONTEND='noninteractive'))
+    container.run('apt', 'clean')
     container.add_label('org.opencontainers.image.url', 'https://github.com/evalf/nutils')
     container.add_label('org.opencontainers.image.source', 'https://github.com/evalf/nutils')
     container.add_label('org.opencontainers.image.authors', 'Evalf')
diff --git a/examples/platewithhole.py b/examples/platewithhole.py
index 48d777650..2d0973dfd 100644
--- a/examples/platewithhole.py
+++ b/examples/platewithhole.py
@@ -80,7 +80,7 @@ def generate(self, radius):
         return topo.withboundary(hole='left', sym='top,bottom', far='right'), geom, nurbsbasis, 5
 
 
-def main(mode: Union[FCM, NURBS] = NURBS,
+def main(mode: Union[FCM, NURBS] = NURBS(),
          radius: float = .5,
          traction: float = .1,
          poisson: float = .3):
diff --git a/nutils/__init__.py b/nutils/__init__.py
index b7c01351c..a2881db04 100644
--- a/nutils/__init__.py
+++ b/nutils/__init__.py
@@ -1,4 +1,4 @@
 'Numerical Utilities for Finite Element Analysis'
 
-__version__ = version = '9a2'
+__version__ = version = '9a3'
 version_name = 'jook-sing'
diff --git a/nutils/points.py b/nutils/points.py
index d84ee6117..9391b9429 100644
--- a/nutils/points.py
+++ b/nutils/points.py
@@ -288,7 +288,7 @@ class ConcatPoints(Points):
     triggering deduplication and resulting in a smaller total point count.
     '''
 
-    def __init__(self, allpoints: Tuple[Points,...], duplicates: FrozenSet[Tuple[Tuple[Integral,Integral],...]]):
+    def __init__(self, allpoints: Tuple[Points,...], duplicates: FrozenSet[Tuple[Tuple[Integral,Integral],...]] = frozenset()):
         assert isinstance(allpoints, tuple) and all(isinstance(p, Points) for p in allpoints), 'allpoints={allpoints!r}'
         assert isinstance(duplicates, frozenset) and all(isinstance(d, tuple) and all(isinstance(n, tuple) and len(n) == 2 and all(isinstance(ni, Integral) for ni in n) for n in d) for d in duplicates), f'duplicates={duplicates!r}'
         self.allpoints = allpoints
diff --git a/nutils/topology.py b/nutils/topology.py
index f918a18f0..105e8dfe5 100644
--- a/nutils/topology.py
+++ b/nutils/topology.py
@@ -2654,7 +2654,7 @@ def locate(self, geom, coords, *, eps=0, skip_missing=False, **kwargs):
             if not mymissing: # no points are missing -> keep existing points object
                 newpoints.append(points_)
             elif len(mymissing) < points_.npoints: # some points are missing -> create new CoordsPoints object
-                newpoints.append(points.CoordsPoints(points_.coords[~numeric.asboolean(mymissing, points_.npoints)]))
+                newpoints.append(points.CoordsPoints(types.arraydata(points_.coords[~numeric.asboolean(mymissing, points_.npoints)])))
             else: # all points are missing -> remove element from return sample
                 selection[isampleelem] = False
             del missing[:len(mymissing)]
diff --git a/tests/test_topology.py b/tests/test_topology.py
index 7f8dba317..5d1308edf 100644
--- a/tests/test_topology.py
+++ b/tests/test_topology.py
@@ -943,8 +943,12 @@ def test_invalidargs(self):
             self.domain.locate(self.geom, target, eps=1e-15, tol=1e-12, arguments=dict(scale=.123))
 
     def test_invalidpoint(self):
-        target = numpy.array([(.3, 1), (.2, .3), (.1, .9), (0, 1), (.1, .3)])
-        # the first point is outside the domain, but inside basetopo for mode==trimmed
+        target = numpy.array([(.3, .3), (.21, 1), (.2, 1), (.1, .9), (0, 1), (.1, .3), (.3, .3)])
+        # The first two points are outside the domain, but inside basetopo for
+        # mode==trimmed, triggering a post-processing by SubsetTopology.locate.
+        # Moreover, the second point is in the same basetopo element as the
+        # third, which requires the formation of a new CoordsPoints, whereas
+        # the element of the first point can be dropped altogether.
         with self.subTest('skip_missing=False'), self.assertRaises(topology.LocateError):
             self.domain.locate(self.geom, target, eps=1e-15, tol=1e-12, arguments=dict(scale=.123))
         with self.subTest('skip_missing=True'):