diff --git a/scripts/monitor_dbus_signals.py b/scripts/monitor_dbus_signals.py
index 7810cc6..289fad8 100755
--- a/scripts/monitor_dbus_signals.py
+++ b/scripts/monitor_dbus_signals.py
@@ -731,7 +731,11 @@ def _check():
         print(os.linesep.join(_CALLBACK_ERRORS))
         sys.exit(3)
 
-    result = _check()
+    try:
+        result = _check()
+    except Exception as exco:  # pylint: disable=broad-except
+        print(f"{exco}")
+        sys.exit(4)
 
     assert isinstance(result, list)
     if not result:
diff --git a/testlib/infra.py b/testlib/infra.py
index 27aac90..812653e 100644
--- a/testlib/infra.py
+++ b/testlib/infra.py
@@ -472,6 +472,13 @@ def run_check(self, stop_time):
                     f'stdout: {stdoutdata.decode("utf-8")}'
                 )
 
+            if self.trace.returncode == 4:
+                raise RuntimeError(
+                    "Failure while comparing D-Bus states: "
+                    f'stderr: {stderrdata.decode("utf-8")}, '
+                    f'stdout: {stdoutdata.decode("utf-8")}'
+                )
+
             msg = stdoutdata.decode("utf-8")
             self.assertEqual(
                 self.trace.returncode,