diff --git a/MANIFEST.in b/MANIFEST.in
index 94a21b0..391318d 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -5,7 +5,7 @@ include tox.ini
 include runtests.py
 include rest_captcha/captcha_py2.png
 include rest_captcha/captcha_py3.png
-recursive-include rest_captch/fonts *
+include rest_captcha/fonts *
 global-exclude *pyc
 global-exclude coverage.xml
 global-exclude .DS_Store
diff --git a/rest_captcha/utils.py b/rest_captcha/utils.py
index 300042b..a555bd9 100644
--- a/rest_captcha/utils.py
+++ b/rest_captcha/utils.py
@@ -11,7 +11,7 @@ def get_cache_key(captcha_key):
 
 
 def random_char_challenge(length):
-    chars = 'abcdefghijklmnopqrstuvwxyz'
+    chars = 'abcdefghijklmnopqrstuvwxyz1234567890'
     ret = ''
     for i in range(length):
         ret += random.choice(chars)