diff --git a/freepost/__init__.py b/freepost/__init__.py
index 3431014..a0bd7a5 100644
--- a/freepost/__init__.py
+++ b/freepost/__init__.py
@@ -37,8 +37,8 @@ template = functools.partial (
             # TODO this should be renamed. It's only a way to pretty print dates
             'title': lambda date: dateutil.parser.parse(date).strftime('%b %-d, %Y - %H:%M%z%Z'),
             # Convert markdown to plain text
-            'md2txt': lambda text: bleach.clean (markdown.markdown (text),
-                                                 tags=[], attributes={}, styles=[], strip=True),
+            'md2txt': lambda text: bleach.clean (markdown.markdown(text),
+                                                 tags=[], attributes={}, strip=True),
             # Convert markdown to html
             'md2html': lambda text: bleach.clean (bleach.linkify (markdown.markdown (
                                         text,
@@ -66,7 +66,8 @@ template = functools.partial (
 # "bleach" library is used to sanitize the HTML output of jinja2's "md2html"
 # filter. The library has only a very restrictive list of white-listed
 # tags, so we add some more here.
-bleach.sanitizer.ALLOWED_TAGS += [ 'br', 'img', 'p', 'pre', 'h1', 'h2', 'h3', 'hr' ]
+# The list() casting is required because it's of type "frozenlist"
+bleach.sanitizer.ALLOWED_TAGS = list(bleach.sanitizer.ALLOWED_TAGS) + [ 'br', 'img', 'p', 'pre', 'h1', 'h2', 'h3', 'hr' ]
 bleach.sanitizer.ALLOWED_ATTRIBUTES.update ({
     'img': [ 'src' ]
 })