diff --git a/requirements.txt b/requirements.txt
index aa50fe15..a47fd0da 100755
--- a/requirements.txt
+++ b/requirements.txt
@@ -9,6 +9,7 @@ zeroc-ice
 slugify
 requests-oauthlib
 sleekxmpp
+redis
 
 # Django Stuff #
 django>=1.10,<2.0
diff --git a/services/managers/eve_api_manager.py b/services/managers/eve_api_manager.py
index ea7c7f94..304027ae 100644
--- a/services/managers/eve_api_manager.py
+++ b/services/managers/eve_api_manager.py
@@ -322,8 +322,8 @@ class EveApiManager:
             chars = EveApiManager.get_characters_from_api(api_id, api_key).result
         except evelink.api.APIError as e:
             if int(e.code) in [221, 222]:
-                raise e
-            raise EveApiManager.ApiInvalidError(api_id)
+                raise EveApiManager.ApiInvalidError(api_id)
+            raise e
         except (requests.exceptions.RequestExeception, HTTPError, URLError) as e:
             raise EveApiManager.ApiServerUnreachableError(e)
         except Exception:
diff --git a/services/tasks.py b/services/tasks.py
index 5ceb0571..9789a887 100644
--- a/services/tasks.py
+++ b/services/tasks.py
@@ -25,9 +25,38 @@ from notifications import notify
 from celery.task import periodic_task
 from celery.task.schedules import crontab
 from eveonline.managers import EveManager
+import redis
+
+REDIS_CLIENT = redis.Redis()
 
 logger = logging.getLogger(__name__)
 
+# http://loose-bits.com/2010/10/distributed-task-locking-in-celery.html
+def only_one(function=None, key="", timeout=None):
+    """Enforce only one celery task at a time."""
+
+    def _dec(run_func):
+        """Decorator."""
+
+        def _caller(*args, **kwargs):
+            """Caller."""
+            ret_value = None
+            have_lock = False
+            lock = REDIS_CLIENT.lock(key, timeout=timeout)
+            try:
+                have_lock = lock.acquire(blocking=False)
+                if have_lock:
+                    ret_value = run_func(*args, **kwargs)
+            finally:
+                if have_lock:
+                    lock.release()
+
+            return ret_value
+
+        return _caller
+
+    return _dec(function) if function is not None else _dec
+
 
 @periodic_task(run_every=crontab(minute="*/30"))
 def run_ts3_group_update():
@@ -410,6 +439,7 @@ def update_all_teamspeak3_groups():
 
 
 @task(bind=True)
+@only_one(key="Discord", timeout=60*5)
 def update_discord_groups(self, pk):
     user = User.objects.get(pk=pk)
     logger.debug("Updating discord groups for user %s" % user)
@@ -459,6 +489,7 @@ def update_all_discord_nicknames():
 
 
 @task(bind=True)
+@only_one(key="Discourse", timeout=60*5)
 def update_discourse_groups(self, pk):
     user = User.objects.get(pk=pk)
     logger.debug("Updating discourse groups for user %s" % user)