diff --git a/flashtext/keyword.py b/flashtext/keyword.py
index f358c77..f21e3e1 100644
--- a/flashtext/keyword.py
+++ b/flashtext/keyword.py
@@ -45,10 +45,10 @@ def __init__(self, case_sensitive=False):
         self._white_space_chars = set(['.', '\t', '\n', '\a', ' ', ','])
         try:
             # python 2.x
-            self.non_word_boundaries = set(string.digits + string.letters + '_')
+            self.non_word_boundaries = set('_')
         except AttributeError:
             # python 3.x
-            self.non_word_boundaries = set(string.digits + string.ascii_letters + '_')
+            self.non_word_boundaries = set('_')
         self.keyword_trie_dict = dict()
         self.case_sensitive = case_sensitive
         self._terms_in_trie = 0