diff --git a/setup.py b/setup.py
index 42669b9..bcc47c0 100644
--- a/setup.py
+++ b/setup.py
@@ -9,5 +9,5 @@ setup(
     version='0.1',
     requires=['matplotlib'],
     package_data={'tudplot': ['tud.mplstyle']},
-    zip_safe=True,
+    zip_safe=False,
 )
diff --git a/tudplot/xmgrace.py b/tudplot/xmgrace.py
index 4594a49..8833d96 100755
--- a/tudplot/xmgrace.py
+++ b/tudplot/xmgrace.py
@@ -4,14 +4,21 @@ import logging
 from collections import OrderedDict
 
 from matplotlib.colors import ColorConverter
-from matplotlib.cbook import is_string_like
+#from matplotlib.cbook import is_string_like
 import numpy as np
 import matplotlib as mpl
+import six
 
 from .tud import tudcolors
 from .tex2grace import latex_to_xmgrace
 
 
+def is_string_like(obj):
+    """Return True if *obj* looks like a string"""
+    # (np.str_ == np.unicode_ on Py3).
+    return isinstance(obj, (six.string_types, np.str_, np.unicode_))
+
+
 def indexed(list, default=None):
     def index(arg):
         for i, v in enumerate(list):