diff --git a/ccserver/exceptions.py b/ccserver/exceptions.py
index efdf16361cb3b8b31a4fa8c0e8b8e4faa84ae62b..565b0729da0ce024db4eb8cfc7d1f525580a40d7 100644
--- a/ccserver/exceptions.py
+++ b/ccserver/exceptions.py
@@ -35,3 +35,6 @@ class BadJobTypeError(Exception):
 
 class UnknownJobError(Exception):
     pass
+
+class UnknownObjectError(Exception):
+    pass
diff --git a/ccserver/objectsdb.py b/ccserver/objectsdb.py
index 73380707b4cb871486421e3a2ff95378cbc81cf5..efab3f7144f36b8cfb9be5f645e6c83a37efd657 100644
--- a/ccserver/objectsdb.py
+++ b/ccserver/objectsdb.py
@@ -13,7 +13,7 @@ from threading import RLock
 
 from ccserver.tql import TqlObject
 from ccserver.orderedset import OrderedSet
-from ccserver.exceptions import AlreadyRegistered
+from ccserver.exceptions import AlreadyRegistered, UnknownObjectError
 
 DEFAULT_TTL = 0
 TTL_SERVER_DELTA = 1 # Delta to apply for all tags
@@ -107,7 +107,8 @@ class ObjectsDB(object):
             oid = ids.pop()
             obj = self._objects.get(oid)
 
-            assert obj is not None, 'object not found'
+            if obj is None:
+                raise UnknownObjectError('%r not found in database' % oid)
 
             if '__parent' in obj:
                 # Current object is proxified by a parent: