diff --git a/aiida/cmdline/utils/log.py b/aiida/cmdline/utils/log.py
index dbc715e7ad..69b7c7d11e 100644
--- a/aiida/cmdline/utils/log.py
+++ b/aiida/cmdline/utils/log.py
@@ -51,7 +51,15 @@ def format(record):
         except KeyError:
             fg = 'white'
 
-        if record.prefix:
+        try:
+            prefix = record.prefix
+        except AttributeError:
+            prefix = None
+
+        if prefix:
             return f'{click.style(record.levelname.capitalize(), fg=fg, bold=True)}: {record.msg % record.args}'
 
-        return f'{record.msg % record.args}'
+        if record.args:
+            return f'{record.msg % record.args}'
+
+        return record.msg
diff --git a/tests/cmdline/utils/test_log.py b/tests/cmdline/utils/test_log.py
new file mode 100644
index 0000000000..a5166f75e0
--- /dev/null
+++ b/tests/cmdline/utils/test_log.py
@@ -0,0 +1,43 @@
+# -*- coding: utf-8 -*-
+###########################################################################
+# Copyright (c), The AiiDA team. All rights reserved.                     #
+# This file is part of the AiiDA code.                                    #
+#                                                                         #
+# The code is hosted on GitHub at https://github.com/aiidateam/aiida-core #
+# For further information on the license, see the LICENSE.txt file        #
+# For further information please visit http://www.aiida.net               #
+###########################################################################
+"""Tests for the :mod:`aiida.cmdline.utils.log` module."""
+import logging
+
+from aiida.cmdline.utils import log
+
+
+def test_cli_formatter():
+    """Test the ``CliFormatter.format`` method for a plain message.
+
+    Note that if it contains percentage signs but no arguments, it should not try to convert it.
+    """
+    message = 'message'
+    record = logging.LogRecord('name', logging.INFO, 'pathname', 0, message, (), 'exc_info')
+    assert log.CliFormatter.format(record) == message
+
+
+def test_cli_formatter_no_args():
+    """Test the ``CliFormatter.format`` method for a message with percentage signs but no args."""
+    message = 'PID    MEM %    CPU %  started'
+    record = logging.LogRecord('name', logging.INFO, 'pathname', 0, message, (), 'exc_info')
+    assert log.CliFormatter.format(record) == message
+
+
+def test_cli_formatter_args():
+    """Test the ``CliFormatter.format`` method for a message with a single argument."""
+    record = logging.LogRecord('name', logging.INFO, 'pathname', 0, 'Some %s', ('value',), 'exc_info')
+    assert log.CliFormatter.format(record) == 'Some value'
+
+
+def test_cli_formatter_prefix():
+    """Test the ``CliFormatter.format`` method for a message with a single argument."""
+    record = logging.LogRecord('name', logging.INFO, 'pathname', 0, 'Some %s', ('value',), 'exc_info')
+    record.prefix = True
+    assert log.CliFormatter.format(record) == '\x1b[34m\x1b[1mInfo\x1b[0m: Some value'