diff --git a/luigi/worker.py b/luigi/worker.py
index 8a00fdb246..b75595368e 100644
--- a/luigi/worker.py
+++ b/luigi/worker.py
@@ -124,7 +124,8 @@ class TaskProcess(multiprocessing.Process):
     }
 
     def __init__(self, task, worker_id, result_queue, status_reporter,
-                 use_multiprocessing=False, worker_timeout=0, check_unfulfilled_deps=True):
+                 use_multiprocessing=False, worker_timeout=0, check_unfulfilled_deps=True,
+                 check_complete_on_run=False):
         super(TaskProcess, self).__init__()
         self.task = task
         self.worker_id = worker_id
@@ -134,6 +135,7 @@ def __init__(self, task, worker_id, result_queue, status_reporter,
         self.timeout_time = time.time() + self.worker_timeout if self.worker_timeout else None
         self.use_multiprocessing = use_multiprocessing or self.timeout_time is not None
         self.check_unfulfilled_deps = check_unfulfilled_deps
+        self.check_complete_on_run = check_complete_on_run
 
     def _run_get_new_deps(self):
         task_gen = self.task.run()
@@ -186,8 +188,6 @@ def run(self):
 
             if _is_external(self.task):
                 # External task
-                # TODO(erikbern): We should check for task completeness after non-external tasks too!
-                # This will resolve #814 and make things a lot more consistent
                 if self.task.complete():
                     status = DONE
                 else:
@@ -197,7 +197,13 @@ def run(self):
             else:
                 with self._forward_attributes():
                     new_deps = self._run_get_new_deps()
-                status = DONE if not new_deps else PENDING
+                if not new_deps:
+                    if not self.check_complete_on_run or self.task.complete():
+                        status = DONE
+                    else:
+                        raise TaskException("Task finished running, but complete() is still returning false.")
+                else:
+                    status = PENDING
 
             if new_deps:
                 logger.info(
@@ -215,15 +221,17 @@ def run(self):
             raise
         except BaseException as ex:
             status = FAILED
-            logger.exception("[pid %s] Worker %s failed    %s", os.getpid(), self.worker_id, self.task)
-            self.task.trigger_event(Event.FAILURE, self.task, ex)
-            raw_error_message = self.task.on_failure(ex)
-            expl = raw_error_message
+            expl = self._handle_run_exception(ex)
 
         finally:
             self.result_queue.put(
                 (self.task.task_id, status, expl, missing, new_deps))
 
+    def _handle_run_exception(self, ex):
+        logger.exception("[pid %s] Worker %s failed    %s", os.getpid(), self.worker_id, self.task)
+        self.task.trigger_event(Event.FAILURE, self.task, ex)
+        return self.task.on_failure(ex)
+
     def _recursive_terminate(self):
         import psutil
 
@@ -447,6 +455,10 @@ class worker(Config):
     check_unfulfilled_deps = BoolParameter(default=True,
                                            description='If true, check for completeness of '
                                            'dependencies before running a task')
+    check_complete_on_run = BoolParameter(default=False,
+                                          description='If true, only mark tasks as done after running if they are complete. '
+                                          'Regardless of this setting, the worker will always check if external '
+                                          'tasks are complete before marking them as done.')
     force_multiprocessing = BoolParameter(default=False,
                                           description='If true, use multiprocessing also when '
                                           'running with 1 worker')
@@ -1016,6 +1028,7 @@ def _create_task_process(self, task):
             use_multiprocessing=use_multiprocessing,
             worker_timeout=self._config.timeout,
             check_unfulfilled_deps=self._config.check_unfulfilled_deps,
+            check_complete_on_run=self._config.check_complete_on_run,
         )
 
     def _purge_children(self):
diff --git a/test/helpers.py b/test/helpers.py
index c407835e30..64911a06e4 100644
--- a/test/helpers.py
+++ b/test/helpers.py
@@ -138,6 +138,13 @@ def run(self):
         self.comp = True
 
 
+# string subclass that matches arguments containing the specified substring
+# for use in mock 'called_with' assertions
+class StringContaining(str):
+    def __eq__(self, other_str):
+        return self in other_str
+
+
 class LuigiTestCase(unittest.TestCase):
     """
     Tasks registred within a test case will get unregistered in a finalizer
diff --git a/test/worker_task_test.py b/test/worker_task_test.py
index c0355fb9e9..5196210296 100644
--- a/test/worker_task_test.py
+++ b/test/worker_task_test.py
@@ -18,7 +18,7 @@
 from subprocess import check_call
 import sys
 
-from helpers import LuigiTestCase
+from helpers import LuigiTestCase, StringContaining
 import mock
 from psutil import Process
 from time import sleep
@@ -87,6 +87,25 @@ def on_failure(self, exception):
             task_process.run()
             mock_put.assert_called_once_with((task.task_id, FAILED, "test failure expl", [], []))
 
+    def test_fail_on_false_complete(self):
+        class NeverCompleteTask(luigi.Task):
+            def complete(self):
+                return False
+
+        task = NeverCompleteTask()
+        result_queue = multiprocessing.Queue()
+        task_process = TaskProcess(task, 1, result_queue, mock.Mock(), check_complete_on_run=True)
+
+        with mock.patch.object(result_queue, 'put') as mock_put:
+            task_process.run()
+            mock_put.assert_called_once_with((
+                task.task_id,
+                FAILED,
+                StringContaining("finished running, but complete() is still returning false"),
+                [],
+                None
+            ))
+
     def test_cleanup_children_on_terminate(self):
         """
         Subprocesses spawned by tasks should be terminated on terminate