diff --git a/telegram/document.py b/telegram/document.py
index 1fb21a92c..31dbeab0b 100644
--- a/telegram/document.py
+++ b/telegram/document.py
@@ -65,4 +65,6 @@ class Document(TelegramObject):
         if not data:
             return None
 
+        data['thumb'] = PhotoSize.de_json(data.get('thumb'))
+
         return Document(**data)
diff --git a/telegram/forcereply.py b/telegram/forcereply.py
index b28e8f58c..28057bee9 100644
--- a/telegram/forcereply.py
+++ b/telegram/forcereply.py
@@ -57,4 +57,3 @@ class ForceReply(ReplyMarkup):
             return None
 
         return ForceReply(**data)
-        
diff --git a/telegram/sticker.py b/telegram/sticker.py
index c663a3fed..35bc01674 100644
--- a/telegram/sticker.py
+++ b/telegram/sticker.py
@@ -67,4 +67,6 @@ class Sticker(TelegramObject):
         if not data:
             return None
 
+        data['thumb'] = PhotoSize.de_json(data.get('thumb'))
+
         return Sticker(**data)
diff --git a/telegram/video.py b/telegram/video.py
index b9414835b..b10dd475f 100644
--- a/telegram/video.py
+++ b/telegram/video.py
@@ -74,4 +74,6 @@ class Video(TelegramObject):
         if not data:
             return None
 
+        data['thumb'] = PhotoSize.de_json(data.get('thumb'))
+
         return Video(**data)