diff --git a/qrexec/tests/socket/agent.py b/qrexec/tests/socket/agent.py
index 7b2f873a..1b7dea90 100644
--- a/qrexec/tests/socket/agent.py
+++ b/qrexec/tests/socket/agent.py
@@ -72,6 +72,7 @@ def assertExpectedStdout(self, target, expected_stdout: bytes, *, exit_code=0):
             self.assertTrue(msg_body)
             self.assertEqual(msg_type, qrexec.MSG_DATA_STDOUT)
             stdout_entries.append(msg_body)
+        self.assertEqual(b"".join(stdout_entries), expected_stdout)
 
     def make_executable_service(self, *args):
         util.make_executable_service(self.tempdir, *args)