diff --git a/nutils/expression_v2.py b/nutils/expression_v2.py
index 2a2ea78fd..6d15c4a14 100644
--- a/nutils/expression_v2.py
+++ b/nutils/expression_v2.py
@@ -701,7 +701,7 @@ def define_for(self, __name: str, *, gradient: Optional[str] = None, curl: Optio
                 raise ValueError('The curl can only be defined for a geometry with shape (3,) but got {}.'.format(numpy.shape(geom)))
             # Definition: `curl_ki(u_...)` := `ε_kji ∇_j(u_...)`. Should be used as
             # `curl_ki(u_i)`, which is equivalent to `ε_kji ∇_j(u_i)`.
-            setattr(self, curl, lambda arg: (function.levicivita(3) * function.grad(arg, geom)[..., numpy.newaxis, :, numpy.newaxis]).sum(-2))
+            setattr(self, curl, lambda arg: numpy.sum(function.levicivita(3) * function.grad(arg, geom)[..., numpy.newaxis, :, numpy.newaxis], axis=-2))
         if normal:
             setattr(self, normal, function.normal(geom))
         for i, jacobian in enumerate(jacobians):
diff --git a/nutils/function.py b/nutils/function.py
index 45dd42c5e..02c82a2cb 100644
--- a/nutils/function.py
+++ b/nutils/function.py
@@ -1976,10 +1976,10 @@ def opposite(__arg: IntoArray) -> Array:
     :func:`jump` : the jump at an interface
     '''
 
-    arg = Array.cast(__arg)
+    arg, scale = Array.cast_withscale(__arg)
     for space in sorted(arg.spaces):
         arg = _Opposite(arg, space)
-    return arg
+    return arg * scale
 
 
 def mean(__arg: IntoArray) -> Array:
@@ -2009,8 +2009,7 @@ def mean(__arg: IntoArray) -> Array:
     array([ 1.5])
     '''
 
-    arg = Array.cast(__arg)
-    return .5 * (arg + opposite(arg))
+    return .5 * (__arg + opposite(__arg))
 
 
 def jump(__arg: IntoArray) -> Array:
@@ -2046,8 +2045,7 @@ def jump(__arg: IntoArray) -> Array:
     array([ 1.])
     '''
 
-    arg = Array.cast(__arg)
-    return opposite(arg) - arg
+    return opposite(__arg) - __arg
 
 # REDUCTION
 
diff --git a/nutils/sample.py b/nutils/sample.py
index f3f3dfeb7..74d83e03a 100644
--- a/nutils/sample.py
+++ b/nutils/sample.py
@@ -446,7 +446,8 @@ def get_evaluable_indices(self, ielem: evaluable.Array) -> evaluable.Array:
         return evaluable.Range(npoints) + offset
 
     def __call__(self, __func: function.IntoArray) -> function.Array:
-        return _ConcatenatePoints(function.Array.cast(__func), self)
+        func, funcscale = function.Array.cast_withscale(__func)
+        return _ConcatenatePoints(func, self) * funcscale
 
 
 class _CustomIndex(_TransformChainsSample):
@@ -538,8 +539,8 @@ def integral(self, __func: function.IntoArray) -> function.Array:
         return function.zeros(func.shape, func.dtype)
 
     def __call__(self, __func: function.IntoArray) -> function.Array:
-        func = function.Array.cast(__func)
-        return function.zeros((0, *func.shape), func.dtype)
+        func, funcscale = function.Array.cast_withscale(__func)
+        return function.zeros((0, *func.shape), func.dtype) * funcscale
 
     def basis(self) -> function.Array:
         return function.zeros((0,), float)