diff --git a/lib.py b/lib.py
index f482218..61e9f41 100644
--- a/lib.py
+++ b/lib.py
@@ -16,5 +16,5 @@ def cat_words(dictionary=DICTIONARY):
                 # remove end of line
                 word = word[:-1]
                 # filter out five letter words
-                if len(word) == WORD_LENGTH and "'" not in word and not word[0].isupper():
+                if len(word) == WORD_LENGTH and all([letter.isalpha() and letter.islower() for letter in word]):
                     yield word