diff --git a/nutils/function.py b/nutils/function.py
index c00103214..bbd60d719 100644
--- a/nutils/function.py
+++ b/nutils/function.py
@@ -27,7 +27,7 @@
 from typing import Tuple, Union, Type, Callable, Sequence, Any, Optional, Iterator, Iterable, Dict, Mapping, overload, List, Set, FrozenSet
 from . import evaluable, numeric, util, expression, types, warnings, debug_flags
 from .transform import EvaluableTransformChain
-from .transformseq import Transforms
+from .transformseq import Transforms, IdentifierTransforms
 import builtins, numpy, re, types as builtin_types, itertools, functools, operator, abc, numbers
 
 IntoArray = Union['Array', numpy.ndarray, bool, int, float]
@@ -440,6 +440,23 @@ def argshapes(self) -> Mapping[str, Tuple[int, ...]]:
           shapes[arg._name] = tuple(map(int, arg.shape))
     return shapes
 
+class _SetSpace(Array):
+
+  def __init__(self, arg: Array, space: str, value: Array):
+    if space not in arg.spaces:
+      raise ValueError('argument does not depend on space {!r}'.format(space))
+    if value.ndim != 1:
+      raise ValueError('expected one-dimensional coordinate for space {!r}'.format(space))
+    self._space = space
+    self._arg = arg
+    self._value = value
+    super().__init__(shape=arg.shape, dtype=arg.dtype, spaces=arg.spaces-{space})
+
+  def lower(self, points_shape: _PointsShape, transform_chains: _TransformChainsMap, coordinates: _CoordinatesMap) -> evaluable.Array:
+    value = self._value.lower(points_shape, transform_chains, coordinates)
+    chain = IdentifierTransforms(ndims=1, name='dummy', length=value.shape[-1]).get_evaluable(evaluable.asarray(0)) # <- identity
+    return self._arg.lower(points_shape, {self._space: (chain, chain), **transform_chains}, {self._space: value, **coordinates})
+
 class _Unlower(Array):
 
   def __init__(self, array: evaluable.Array, spaces: FrozenSet[str], points_shape: Tuple[evaluable.Array, ...], transform_chains: Tuple[EvaluableTransformChain, ...], coordinates: Tuple[evaluable.Array, ...]) -> None: