diff --git a/job/dispatch.hpp b/job/dispatch.hpp
index fb0ecbde..dfb38e21 100644
--- a/job/dispatch.hpp
+++ b/job/dispatch.hpp
@@ -6,13 +6,13 @@
  * Copyright 2018 Danny Robson <danny@nerdcruft.net>
  */
 
-#ifndef CRUFT_UTIL_JOB_DISPATCH_HPP
-#define CRUFT_UTIL_JOB_DISPATCH_HPP
+#pragma once
 
 #include "queue.hpp"
 
 #include "../extent.hpp"
 #include "../region.hpp"
+#include "../concepts.hpp"
 
 #include <vector>
 
@@ -27,42 +27,54 @@ namespace cruft::job {
     /// if one is supplied.
     ///
     /// TODO: extend to 1d and 3d
+    ///
+    /// \param area  The total size of the work unit
+    /// \param chunk The size of the subdivided units to be send to threads.
     template <
         typename ContainerT,
         typename FunctionT,
-        typename ...Args,
+        typename ...ArgsT,
         size_t DimensionV
     >
+    requires requires (
+        ContainerT t,
+        cruft::point<DimensionV,int> p,
+        FunctionT f,
+        ArgsT ...args
+    ) {
+        { t[p] = std::invoke (f, p, args...) };
+    }
     auto
     dispatch (
         cruft::job::queue &q,
         ContainerT &data,
+        cruft::region<DimensionV,int> total_area,
         cruft::extent<DimensionV,int> chunk,
         FunctionT &&func,
-        Args ...args)
-    {
-        auto chunked_func = [&func] (ContainerT &inner_data,
-                                     auto param,
-                                     Args... inner_args)
-        {
-            for (auto p: param) {
-                if (!inner_data.extent ().exclusive (p))
-                    continue;
+        ArgsT ...args
+    ) {
+        auto chunked_func = [&func] (
+            ContainerT &inner_data,
+            auto param,
+            ArgsT... inner_args
+        ) {
+            for (cruft::point<DimensionV,int> p: param)
                 inner_data[p] = std::invoke (func, p, inner_args...);
-            }
         };
 
         std::vector<queue::cookie> cookies;
 
-        const extent2i count = (data.extent () + chunk - 1) / chunk;
+        extent2i const count = (total_area.e + chunk - 1) / chunk;
 
         for (auto index: count.step ()) {
-            cruft::point<DimensionV,int> base = index * chunk;
+            cruft::point<DimensionV,int> base = index * chunk + total_area.p.template as<cruft::vector> ();
+            region<DimensionV,int> const oversized_work { base, chunk };
+            auto const constrained_work = intersection (oversized_work, total_area);
             cookies.push_back (
                 q.submit (
                     chunked_func,
                     std::ref (data),
-                    cruft::region<DimensionV,int> {base, chunk}.step (),
+                    constrained_work.step (),
                     args...
                 )
             );
@@ -71,5 +83,3 @@ namespace cruft::job {
         return std::tuple (std::forward<FunctionT> (func), std::move (cookies));
     }
 }
-
-#endif
diff --git a/test/job/dispatch.cpp b/test/job/dispatch.cpp
index fceb28e5..8a1ced06 100644
--- a/test/job/dispatch.cpp
+++ b/test/job/dispatch.cpp
@@ -14,39 +14,53 @@
 
 
 ///////////////////////////////////////////////////////////////////////////////
-struct value {
-    template <typename T>
-    void operator= (T &&) { }
-};
+struct container {
+    cruft::point2i
+    operator[] (cruft::point2i p)&
+    { return values.emplace_back () = p; }
 
+    bool is_unique (void)
+    {
+        cruft::coord::ordering<cruft::point2i> comp {};
+        std::sort (values.begin (), values.end (), comp);
+        auto const pos = std::adjacent_find (values.begin (), values.end ());
+        return pos == values.end ();
+    }
 
-//-----------------------------------------------------------------------------
-struct data_t {
-    cruft::extent2i extent (void) const { return { 4, 4 }; }
-    auto operator[] (cruft::point2i) { return value {};};
+    std::size_t size (void) const { return values.size (); }
+
+    std::vector<cruft::point2i> values;
 };
 
 
 //-----------------------------------------------------------------------------
 void test_dispatch_uniqueness (cruft::TAP::logger &tap)
 {
-    std::vector<cruft::point2i> points;
-    data_t data;
+    container store;
+
+    cruft::region2i const work_region {
+        cruft::point2i { 0 },
+        cruft::extent2i { 512 }
+    };
 
     cruft::job::queue q (1, 512  * 512 + 1);
     cruft::job::dispatch (
-        q, data,
+        q, store,
+        work_region,
         cruft::extent2i {2},
-        [&] (cruft::point2i p)
-    {
-        points.push_back (p);
-        return 0;
-    });
+        [] (auto &&arg) { return arg; }
+    );
 
-    cruft::coord::ordering<cruft::point2i> comp {};
-    std::sort (points.begin (), points.end (), comp);
-    auto const pos = std::adjacent_find (points.begin (), points.end ());
-    tap.expect (pos == points.end (), "job::queue indices are unique");
+    tap.expect (
+        store.is_unique (),
+        "job::queue indices are unique"
+    );
+
+    tap.expect_eq (
+        store.size (),
+        std::size_t (work_region.magnitude ().area ()),
+        "job::queue evaluated expected times"
+    );
 }