diff --git a/distarray/dist/decorators.py b/distarray/dist/decorators.py
index 62b7aaa5..98243841 100644
--- a/distarray/dist/decorators.py
+++ b/distarray/dist/decorators.py
@@ -13,8 +13,8 @@
 import functools
 
 from distarray.dist.distarray import DistArray
-from distarray.dist.context import Context
-from distarray.error import ContextError
+from distarray.dist.maps import Distribution
+from distarray.error import DistributionError
 from distarray.utils import has_exactly_one
 
 
@@ -34,29 +34,30 @@ def push_fn(self, context, fn_key, fn):
         """Push function to the engines."""
         context._push({fn_key: fn}, targets=context.targets)
 
-    def determine_context(self, args, kwargs):
-        """ Determine a context from a functions arguments."""
+    def determine_distribution(self, args, kwargs):
+        """ Determine a distribution from a functions arguments."""
 
-        contexts = []
+        dists = []
         # inspect args for a context
         for arg in args + tuple(kwargs.values()):
             if isinstance(arg, DistArray):
-                contexts.append(arg.context)
-            elif isinstance(arg, Context):
-                contexts.append(arg)
+                dists.append(arg.distribution)
+            elif isinstance(arg, Distribution):
+                dists.append(arg)
 
         # check the args had a context
-        if contexts == []:
-            raise TypeError('Function must take DistArray or Context objects.')
+        if dists == []:
+            raise TypeError('Function must take DistArray or Distribution'
+                            ' objects.')
 
         # check that all contexts are equal
-        if not contexts.count(contexts[0]) == len(contexts):
-            msg = ("Arguments must use the same Context (given arguments of "
-                   "type %r)")
-            msg %= (tuple(set(contexts)),)
-            raise ContextError(msg)
+        if not dists.count(dists[0]) == len(dists):
+            msg = ("Arguments must use the same Distribution (given arguments "
+                   "of type %r)")
+            msg %= (tuple(set(dists)),)
+            raise DistributionError(msg)
 
-        return contexts[0]
+        return dists[0]
 
     def key_and_push_args(self, args, kwargs, context=None, da_handler=None):
         """
@@ -76,7 +77,8 @@ def key_and_push_args(self, args, kwargs, context=None, da_handler=None):
         """
 
         if context is None:
-            context = self.determine_context(args, kwargs)
+            distribution = self.determine_distribution(args, kwargs)
+            context = distribution.context
 
         # handle positional arguments
         arg_keys = []
@@ -114,7 +116,7 @@ def key_and_push_args(self, args, kwargs, context=None, da_handler=None):
 
         return arg_str, kwarg_str
 
-    def process_return_value(self, context, result_key):
+    def process_return_value(self, context, targets, result_key):
         """Figure out what to return on the Client.
 
         Parameters
@@ -133,7 +135,7 @@ def process_return_value(self, context, result_key):
         def get_type_str(key):
             return str(type(key))
         result_type_str = context.apply(get_type_str, args=(result_key,),
-                                        targets=context.targets)
+                                        targets=targets)
 
         def is_NoneType(typestring):
             return (typestring == "<type 'NoneType'>" or
@@ -144,11 +146,11 @@ def is_LocalArray(typestring):
                                   "LocalArray'>")
 
         if all(is_LocalArray(r) for r in result_type_str):
-            result = DistArray.from_localarrays(result_key, context=context)
+            result = DistArray.from_localarrays(result_key, context=context, targets=targets)
         elif all(is_NoneType(r) for r in result_type_str):
             result = None
         else:
-            result = context._pull(result_key, targets=context.targets)
+            result = context._pull(result_key, targets=targets)
             if has_exactly_one(result):
                 result = next(x for x in result if x is not None)
 
@@ -160,7 +162,8 @@ class local(DecoratorBase):
 
     def __call__(self, *args, **kwargs):
         # get context from args
-        context = self.determine_context(args, kwargs)
+        distribution = self.determine_distribution(args, kwargs)
+        context = distribution.context
         # push function
         self.push_fn(context, self.fn_key, self.fn)
 
@@ -170,9 +173,9 @@ def __call__(self, *args, **kwargs):
 
         exec_str = "%s = %s(*%s, **%s)"
         exec_str %= (result_key, self.fn_key, args, kwargs)
-        context._execute(exec_str, targets=context.targets)
+        context._execute(exec_str, targets=distribution.targets)
 
-        return self.process_return_value(context, result_key)
+        return self.process_return_value(context, distribution.targets, result_key)
 
 
 class vectorize(DecoratorBase):
@@ -186,12 +189,13 @@ def get_ndarray(self, da, arg_keys):
 
     def __call__(self, *args, **kwargs):
         # get context from args
-        context = self.determine_context(args, kwargs)
+        distribution = self.determine_distribution(args, kwargs)
+        context = distribution.context
         # push function
         self.push_fn(context, self.fn_key, self.fn)
         # vectorize the function
         exec_str = "%s = numpy.vectorize(%s)" % (self.fn_key, self.fn_key)
-        context._execute(exec_str, targets=context.targets)
+        context._execute(exec_str, targets=distribution.targets)
 
         # Find the first distarray, they should all be the same up to the data.
         for arg in args:
@@ -208,5 +212,5 @@ def __call__(self, *args, **kwargs):
                             "%s(*%s, **%s)")
                 exec_str %= (out.key, out.key, self.fn_key, args_str,
                              kwargs_str)
-                context._execute(exec_str, targets=context.targets)
+                context._execute(exec_str, targets=distribution.targets)
                 return out
diff --git a/distarray/dist/tests/test_decorators.py b/distarray/dist/tests/test_decorators.py
index f63107f0..47fa06a9 100644
--- a/distarray/dist/tests/test_decorators.py
+++ b/distarray/dist/tests/test_decorators.py
@@ -21,29 +21,30 @@
 from distarray.dist.context import Context
 from distarray.dist.maps import Distribution
 from distarray.dist.decorators import DecoratorBase, local, vectorize
-from distarray.error import ContextError
+from distarray.error import DistributionError
 
 
 class TestDecoratorBase(TestCase):
 
-    def test_determine_context(self):
+    def test_determine_distribution(self):
         context = Context()
         context2 = Context()  # for cross Context checking
-        distribution = Distribution(context, (2, 2))
-        da = context.ones(distribution)
+        dist = Distribution(context, (2, 2))
+        dist2 = Distribution(context2, (2, 2))
+        da = context.ones(dist)
 
         def dummy_func(*args, **kwargs):
             fn = lambda x: x
             db = DecoratorBase(fn)
-            return db.determine_context(args, kwargs)
+            return db.determine_distribution(args, kwargs)
 
-        self.assertEqual(dummy_func(6, 7, context), context)
-        self.assertEqual(dummy_func('ab', da), context)
-        self.assertEqual(dummy_func(a=da), context)
-        self.assertEqual(dummy_func(context, a=da), context)
+        self.assertEqual(dummy_func(6, 7, dist), dist)
+        self.assertEqual(dummy_func('ab', da), dist)
+        self.assertEqual(dummy_func(a=da), dist)
+        self.assertEqual(dummy_func(dist, a=da), dist)
 
         self.assertRaises(TypeError, dummy_func, 'foo')
-        self.assertRaises(ContextError, dummy_func, context, context2)
+        self.assertRaises(DistributionError, dummy_func, dist, dist2)
 
     def test_key_and_push_args(self):
         context = Context()
@@ -107,8 +108,7 @@ def local_sum(da):
 
     @local
     def call_barrier(da):
-        from mpi4py import MPI
-        MPI.COMM_WORLD.Barrier()
+        da.comm.Barrier()
         return da
 
     @local
@@ -219,15 +219,13 @@ def test_local_add_nums(self):
         self.assert_allclose(df, 2 * numpy.pi + 11 + 12 + 13)
 
     def test_local_add_distarrayproxies(self):
-        distribution = Distribution(self.context, (5, 5))
-        dg = self.context.empty(distribution)
+        dg = self.context.empty(self.da.distribution)
         dg.fill(33)
         dh = self.local_add_distarrayproxies(self.da, dg)
         self.assert_allclose(dh, 33 + 2 * numpy.pi)
 
     def test_local_add_mixed(self):
-        distribution = Distribution(self.context, (5, 5))
-        di = self.context.empty(distribution)
+        di = self.context.empty(self.da.distribution)
         di.fill(33)
         dj = self.local_add_mixed(self.da, 11, di, 12)
         self.assert_allclose(dj, 2 * numpy.pi + 11 + 33 + 12)
@@ -245,10 +243,9 @@ def test_local_add_kwargs(self):
         self.assert_allclose(dl, 2 * numpy.pi + 11 + 12)
 
     def test_local_add_supermix(self):
-        distribution = Distribution(self.context, (5, 5))
-        dm = self.context.empty(distribution)
+        dm = self.context.empty(self.da.distribution)
         dm.fill(22)
-        dn = self.context.empty(distribution)
+        dn = self.context.empty(self.da.distribution)
         dn.fill(44)
         do = self.local_add_supermix(self.da, 11, dm, 33, dc=dn, num3=55)
         expected = 2 * numpy.pi + 11 + 22 + 33 + 44 + 55 + 66
diff --git a/distarray/dist/tests/test_distarray.py b/distarray/dist/tests/test_distarray.py
index b1e10f0e..4e653228 100644
--- a/distarray/dist/tests/test_distarray.py
+++ b/distarray/dist/tests/test_distarray.py
@@ -722,6 +722,22 @@ def test_create_target_subset(self):
         self.assertEqual(len(ddpr), len(subtargets))
 
 
+class TestReductionRegression(ContextTestCase):
+    ''' Separate class necessary b/c need to run on at least 9 engines to exercise
+    regression.
+
+    '''
+
+    ntargets = 9
+
+    def test_reduction(self):
+        """ Tests that GH issue 403 is fixed """
+        arr = numpy.arange(9 * 9).reshape(9, 9)
+        dist = Distribution(self.context, arr.shape, ('b', 'b'), (9, 1))
+        darr = self.context.fromndarray(arr, dist)
+        assert_allclose(darr.sum().tondarray(), arr.sum())
+
+
 class TestReduceMethods(ContextTestCase):
     """Test reduction methods"""
 
diff --git a/distarray/error.py b/distarray/error.py
index 3a08176b..27cac7ca 100644
--- a/distarray/error.py
+++ b/distarray/error.py
@@ -30,3 +30,7 @@ class InvalidRankError(MPIDistArrayError):
 
 class MPICommError(MPIDistArrayError):
     pass
+
+
+class DistributionError(DistArrayError):
+    pass
diff --git a/distarray/local/localarray.py b/distarray/local/localarray.py
index a89d92f3..a2a6505d 100644
--- a/distarray/local/localarray.py
+++ b/distarray/local/localarray.py
@@ -954,7 +954,8 @@ def _basic_reducer(reduce_comm, op, func, args, kwargs, out):
         out_ndarray = out.ndarray
         if out.ndarray.dtype == np.bool:
             out.ndarray.dtype = np.uint8
-    local_reduce = func(*args, **kwargs)
+    # Use asarray() to coerce np scalars to zero-dimensional arrays.
+    local_reduce = np.asarray(func(*args, **kwargs))
     reduce_comm.Reduce(local_reduce, out_ndarray, op=op, root=0)
     return out