diff --git a/beat/backend/python/test/prefix/algorithms/autonomous/invalid_loop_output/1.json b/beat/backend/python/test/prefix/algorithms/autonomous/invalid_loop_output/1.json
new file mode 100644
index 0000000000000000000000000000000000000000..f407f19b5ae4af3108acd9facc5330b62ce806ec
--- /dev/null
+++ b/beat/backend/python/test/prefix/algorithms/autonomous/invalid_loop_output/1.json
@@ -0,0 +1,24 @@
+{
+    "schema_version": 2,
+    "language": "python",
+    "api_version": 2,
+    "type": "loop",
+    "splittable": false,
+    "groups": [
+        {
+            "inputs": {
+                "in": {
+                    "type": "user/single_integer/1"
+                }
+            },
+            "loop": {
+                "input": {
+                    "type": "user/single_integer/1"
+                },
+                "output": {
+                    "type": "user/single_integer/1"
+                }
+            }
+        }
+    ]
+}
diff --git a/beat/backend/python/test/prefix/algorithms/autonomous/invalid_loop_output/1.py b/beat/backend/python/test/prefix/algorithms/autonomous/invalid_loop_output/1.py
new file mode 100644
index 0000000000000000000000000000000000000000..157d8ffd163fee0033b59c8a023119e46ef76e63
--- /dev/null
+++ b/beat/backend/python/test/prefix/algorithms/autonomous/invalid_loop_output/1.py
@@ -0,0 +1,33 @@
+#!/usr/bin/env python
+# vim: set fileencoding=utf-8 :
+
+###############################################################################
+#                                                                             #
+# Copyright (c) 2018 Idiap Research Institute, http://www.idiap.ch/           #
+# Contact: beat.support@idiap.ch                                              #
+#                                                                             #
+# This file is part of the beat.backend.python module of the BEAT platform.   #
+#                                                                             #
+# Commercial License Usage                                                    #
+# Licensees holding valid commercial BEAT licenses may use this file in       #
+# accordance with the terms contained in a written agreement between you      #
+# and Idiap. For further information contact tto@idiap.ch                     #
+#                                                                             #
+# Alternatively, this file may be used under the terms of the GNU Affero      #
+# Public License version 3 as published by the Free Software and appearing    #
+# in the file LICENSE.AGPL included in the packaging of this file.            #
+# The BEAT platform is distributed in the hope that it will be useful, but    #
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY  #
+# or FITNESS FOR A PARTICULAR PURPOSE.                                        #
+#                                                                             #
+# You should have received a copy of the GNU Affero Public License along      #
+# with the BEAT platform. If not, see http://www.gnu.org/licenses/.           #
+#                                                                             #
+###############################################################################
+
+class Algorithm:
+
+    def validate(self, result):
+        value = result.value
+
+        return value < 6
diff --git a/beat/backend/python/test/test_loop_executor.py b/beat/backend/python/test/test_loop_executor.py
index 1878e4285d845d1ae6bc3e106941503929e6ec6b..769ea50b6826e606705737ee9b4606aeabfbbc60 100644
--- a/beat/backend/python/test/test_loop_executor.py
+++ b/beat/backend/python/test/test_loop_executor.py
@@ -43,6 +43,7 @@ from ..loop_executor import Executor as LoopExecutor
 from ..loop_executor import LoopMessageHandler
 from ..executor import Executor
 from ..message_handler import MessageHandler
+from ..exceptions import RemoteException
 
 from ..algorithm import Algorithm
 from ..dataformat import DataFormat
@@ -105,6 +106,7 @@ class TestExecution(unittest.TestCase):
         self.message_handler = None
         self.loop_message_handler = None
         self.executor_socket = None
+        self.loop_executor = None
         self.loop_socket = None
         self.zmq_context = None
 
@@ -114,6 +116,9 @@ class TestExecution(unittest.TestCase):
         shutil.rmtree(self.working_dir)
         shutil.rmtree(self.loop_working_dir)
 
+        if self.loop_executor:
+            self.loop_executor.wait()
+
         for handler in [self.message_handler, self.loop_message_handler]:
             if handler is not None:
                 handler.kill()
@@ -201,15 +206,16 @@ class TestExecution(unittest.TestCase):
         self.loop_socket = self.zmq_context.socket(zmq.PAIR)
         self.loop_socket.connect(self.loop_message_handler.address)
 
-        loop_executor = LoopExecutor(self.loop_message_handler, self.loop_working_dir, cache_root=self.cache_root)
-        self.assertTrue(loop_executor.setup())
-        self.assertTrue(loop_executor.prepare())
-        loop_executor.process()
+        self.loop_executor = LoopExecutor(self.loop_message_handler, self.loop_working_dir, cache_root=self.cache_root)
+        self.assertTrue(self.loop_executor.setup())
+        self.assertTrue(self.loop_executor.prepare())
+        self.loop_executor.process()
 
         executor = Executor(self.executor_socket, self.working_dir, cache_root=self.cache_root, loop_socket=self.loop_socket)
 
         self.assertTrue(executor.setup())
         self.assertTrue(executor.prepare())
+
         self.assertTrue(executor.process())
 
         cached_file = CachedDataSource()
@@ -225,4 +231,9 @@ class TestExecution(unittest.TestCase):
 
     def test_autonomous_loop(self):
         self.process('autonomous/loop_user/1',
-                     'autonomous/loop/1')
\ No newline at end of file
+                     'autonomous/loop/1')
+
+    def test_autonomous_loop_invalid_output(self):
+        with self.assertRaises(RemoteException):
+            self.process('autonomous/loop_user/1',
+                         'autonomous/invalid_loop_output/1')
\ No newline at end of file