diff --git a/tests/test_activation.py b/tests/test_activation.py
index c2bab42e..f298acc9 100644
--- a/tests/test_activation.py
+++ b/tests/test_activation.py
@@ -1,6 +1,6 @@
 from django.test import TestCase
 
-from viewflow import activation, flow
+from viewflow import activation, flow, lock
 from viewflow.activation import STATUS
 from viewflow.compat import mock
 
@@ -16,6 +16,7 @@ def active_tasks(self):
             return []
 
         def save(self):
+            self.pk = 1
             return
 
     ProcessStub._default_manager.get.return_value = ProcessStub()
@@ -34,6 +35,7 @@ def leading(self):
             return Task.objects.none()
 
         def save(self):
+            self.pk = 1
             return
 
     class UserStub(object):
@@ -42,6 +44,7 @@ class UserStub(object):
     def init_node(self, node):
         class FlowStub(object):
             process_cls = Test.ProcessStub
+            lock_impl = staticmethod(lock.no_lock)
             task_cls = Test.TaskStub
             instance = None
 
diff --git a/tests/test_flow_func.py b/tests/test_flow_func.py
index cc294af2..cf529d06 100644
--- a/tests/test_flow_func.py
+++ b/tests/test_flow_func.py
@@ -178,6 +178,7 @@ def active_tasks(self):
         return []
 
     def save(self):
+        self.pk = 1
         return
 
 
@@ -197,6 +198,7 @@ def leading(self):
         return Task.objects.none()
 
     def save(self):
+        self.pk = 1
         return
 
 
diff --git a/viewflow/activation.py b/viewflow/activation.py
index bbef4293..802abffa 100644
--- a/viewflow/activation.py
+++ b/viewflow/activation.py
@@ -212,6 +212,7 @@ class StartActivation(Activation):
 
     @Activation.status.super()
     def initialize(self, flow_task, task):
+        self.lock = None
         self.flow_task, self.flow_cls = flow_task, flow_task.flow_cls
 
         if task:
@@ -249,6 +250,10 @@ def done(self):
 
         self.process.save()
 
+        lock_impl = self.flow_cls.lock_impl(self.flow_cls.instance)
+        self.lock = lock_impl(self.flow_cls, self.process.pk)
+        self.lock.__enter__()
+
         self.task.process = self.process
         self.task.finished = now()
         self.task.save()
diff --git a/viewflow/decorators.py b/viewflow/decorators.py
index 051e3625..e5bb8833 100644
--- a/viewflow/decorators.py
+++ b/viewflow/decorators.py
@@ -1,3 +1,4 @@
+import sys
 import traceback
 import functools
 
@@ -10,9 +11,13 @@
 def flow_start_func(func):
     @functools.wraps(func)
     def _wrapper(flow_task, *args, **kwargs):
-        activation = flow_task.activation_cls()
-        activation.initialize(flow_task, None)
-        return func(activation, *args, **kwargs)
+        try:
+            activation = flow_task.activation_cls()
+            activation.initialize(flow_task, None)
+            return func(activation, *args, **kwargs)
+        finally:
+            if activation.lock:
+                activation.lock.__exit__(*sys.exc_info())
     return _wrapper
 
 
@@ -102,9 +107,13 @@ def _wrapper(*args, **kwargs):
 def flow_start_signal(handler):
     @functools.wraps(handler)
     def _wrapper(sender, flow_task=None, **signal_kwargs):
-        activation = flow_task.activation_cls()
-        activation.initialize(flow_task, None)
-        return handler(sender=sender, activation=activation, **signal_kwargs)
+        try:
+            activation = flow_task.activation_cls()
+            activation.initialize(flow_task, None)
+            return handler(sender=sender, activation=activation, **signal_kwargs)
+        finally:
+            if activation.lock:
+                activation.lock.__exit__(*sys.exc_info())
     return _wrapper
 
 
@@ -136,14 +145,17 @@ def flow_start_view(view):
 
     @functools.wraps(view)
     def _wrapper(request, flow_cls, flow_task, **kwargs):
+        try:
             activation = flow_task.activation_cls()
             activation.initialize(flow_task, None)
 
             request.activation = activation
             request.process = activation.process
             request.task = activation.task
-
             return view(request, **kwargs)
+        finally:
+            if activation.lock:
+                activation.lock.__exit__(*sys.exc_info())
     return _wrapper