diff --git a/telethon/extensions/html.py b/telethon/extensions/html.py
index bcbd13cc..d4233473 100644
--- a/telethon/extensions/html.py
+++ b/telethon/extensions/html.py
@@ -121,6 +121,9 @@ def parse(html):
     :param message: the message with HTML to be parsed.
     :return: a tuple consisting of (clean message, [message entities]).
     """
+    if not html:
+        return html, []
+
     parser = HTMLToTelegramParser()
     parser.feed(_add_surrogate(html))
     return _del_surrogate(parser.text), parser.entities
@@ -135,7 +138,7 @@ def unparse(text, entities):
     :param entities: the MessageEntity's applied to the text.
     :return: a HTML representation of the combination of both inputs.
     """
-    if not entities:
+    if not text or not entities:
         return text
 
     text = _add_surrogate(text)
diff --git a/telethon/extensions/markdown.py b/telethon/extensions/markdown.py
index a7af1fa8..cb54c99e 100644
--- a/telethon/extensions/markdown.py
+++ b/telethon/extensions/markdown.py
@@ -36,6 +36,9 @@ def parse(message, delimiters=None, url_re=None):
     :param url_re: the URL bytes regex to be used. Must have two groups.
     :return: a tuple consisting of (clean message, [message entities]).
     """
+    if not message:
+        return message, []
+
     if url_re is None:
         url_re = DEFAULT_URL_RE
     elif isinstance(url_re, str):
@@ -137,7 +140,7 @@ def unparse(text, entities, delimiters=None, url_fmt=None):
     :param entities: the MessageEntity's applied to the text.
     :return: a markdown-like text representing the combination of both inputs.
     """
-    if not entities:
+    if not text or not entities:
         return text
 
     if not delimiters: