diff --git a/metaopt/invoker/dualthread.py b/metaopt/invoker/dualthread.py
index 1747743..58d1424 100644
--- a/metaopt/invoker/dualthread.py
+++ b/metaopt/invoker/dualthread.py
@@ -105,15 +105,16 @@ def wait(self):
 
     @stoppable_method
     @stopping_method
-    def stop(self):
+    def stop(self, reason=None):
         """Stops this invoker."""
         with self.lock:
             self.aborted = True
 
-        self.stop_task(self.current_task)
+        self.stop_task(self.current_task, reason=reason)
 
-    def stop_task(self, task):
+    def stop_task(self, task, reason=None):
         """Stops the given task."""
+        del reason  # TODO
         with self.lock:
             if self.call_handle is not task:
                 return
diff --git a/metaopt/invoker/multiprocess.py b/metaopt/invoker/multiprocess.py
index acab453..c1d780a 100644
--- a/metaopt/invoker/multiprocess.py
+++ b/metaopt/invoker/multiprocess.py
@@ -228,7 +228,7 @@ def stop_call(self, call_id, reason):
 
     @stoppable_method
     @stopping_method
-    def stop(self):
+    def stop(self, reason=None):
         """
         Terminates all worker processes for immediate shutdown.
 
@@ -242,6 +242,6 @@ def stop(self):
                 outcome = self._status_db.wait_for_one_outcome()
                 self._handle_outcome(outcome=outcome)
 
-            self._status_db.stop()
+            self._status_db.stop(reason=reason)
 
             self._manager.shutdown()
diff --git a/metaopt/invoker/pluggable.py b/metaopt/invoker/pluggable.py
index 5a624af..1217c10 100644
--- a/metaopt/invoker/pluggable.py
+++ b/metaopt/invoker/pluggable.py
@@ -127,6 +127,6 @@ def wait(self):
 
     @stoppable_method
     @stopping_method
-    def stop(self):
+    def stop(self, reason=None):
         """Stops this invoker."""
-        self._invoker.stop()
+        self._invoker.stop(reason=reason)
diff --git a/metaopt/invoker/simple_multiprocess.py b/metaopt/invoker/simple_multiprocess.py
index 1451bb3..2b818e7 100644
--- a/metaopt/invoker/simple_multiprocess.py
+++ b/metaopt/invoker/simple_multiprocess.py
@@ -117,7 +117,8 @@ def call_on_result(self, result):
         actual_result = result.actual_result
         caller.on_result(actual_result, worker_fargs, **worker_kwargs)
 
-    def stop(self):
+    def stop(self, reason=None):
+        del reason  # TODO
         self.result_queue.put(None)
 
 
diff --git a/metaopt/invoker/singleprocess.py b/metaopt/invoker/singleprocess.py
index 6596e13..d313721 100644
--- a/metaopt/invoker/singleprocess.py
+++ b/metaopt/invoker/singleprocess.py
@@ -41,6 +41,7 @@ def wait(self):
 
     @stoppable_method
     @stopping_method
-    def stop(self):
+    def stop(self, reason=None):
         """Stops this invoker."""
+        del reason  # TODO
         raise NotImplementedError()
diff --git a/metaopt/invoker/util/status_db.py b/metaopt/invoker/util/status_db.py
index 65d9d42..22fd306 100644
--- a/metaopt/invoker/util/status_db.py
+++ b/metaopt/invoker/util/status_db.py
@@ -199,7 +199,7 @@ def _empty_queue_outcome(self):
             self._handle_outcome(outcome)
 
     @stopping_method
-    def stop(self):
+    def stop(self, reason=None):
         """"""
         self._empty_queue_task()
         assert self._queue_task.empty()
@@ -222,7 +222,7 @@ def stop(self):
         for task in self._call_status_dict.values():
             if not isinstance(task, Task):
                 continue
-            release = Release(worker_id=None, call=task.call, value='release')
+            release = Release(worker_id=None, call=task.call, value=reason)
             self._queue_outcome.put(release)
 
         while not self._queue_outcome.empty():
diff --git a/metaopt/util/stoppable.py b/metaopt/util/stoppable.py
index c1a71af..9b9f8b5 100644
--- a/metaopt/util/stoppable.py
+++ b/metaopt/util/stoppable.py
@@ -12,7 +12,7 @@ class BaseStoppable(object):
     __metaclass__ = ABCMeta
 
     @abstractmethod
-    def stop(self):
+    def stop(self, reason=None):
         """
         Stops this object.
 
@@ -81,7 +81,7 @@ def __init__(self):
 
     @stoppable_method
     @stopping_method
-    def stop(self):
+    def stop(self, reason=None):
         """"Stops this object."""
         pass  # implementations may overwrite this method or check for .stopped