diff --git a/ipaacalib/python/src/ipaaca/util/logger.py b/ipaacalib/python/src/ipaaca/util/logger.py
index d8c48524fa5ffed4e08ff7cdad1f029663be8e02..8d5d1cedf15a63c4dfed299998ec9d9b5a06d88d 100644
--- a/ipaacalib/python/src/ipaaca/util/logger.py
+++ b/ipaacalib/python/src/ipaaca/util/logger.py
@@ -5,7 +5,7 @@
 #  "Incremental Processing Architecture
 #   for Artificial Conversational Agents".
 #
-# Copyright (c) 2009-2015 Social Cognitive Systems Group
+# Copyright (c) 2009-2019 Social Cognitive Systems Group
 #                         CITEC, Bielefeld University
 #
 # http://opensource.cit-ec.de/projects/ipaaca/
@@ -43,6 +43,7 @@ import uuid
 
 import ipaaca
 import ipaaca.misc
+import six
 
 
 __all__ = [
@@ -124,7 +125,7 @@ def logger_set_log_level(level=LogLevel.DEBUG):
 	with LOGGER_LOCK:
 		if level in LogLevel._values:
 			CURRENT_LOG_LEVEL = level
-		elif isinstance(level, basestring) and level.upper() in LOG_LEVEL_FROM_STRING_DICT:
+		elif isinstance(level, six.string_types) and level.upper() in LOG_LEVEL_FROM_STRING_DICT:
 			CURRENT_LOG_LEVEL = LOG_LEVEL_FROM_STRING_DICT[level.upper()]
 		else:
 			pass # leave previous setting untouched
@@ -153,7 +154,7 @@ def LOG_IPAACA(lvl, text, now=0.0, fn='???', thread='???'):
 
 
 def LOG_CONSOLE(lvlstr, msg, fn_markup='', msg_markup='', now=0.0, fn='???', thread='???'):
-	if isinstance(msg, basestring):
+	if isinstance(msg, six.string_types):
 		lines = msg.split('\n')
 	else:
 		lines = [msg]