diff --git a/optional-requirements.txt b/optional-requirements.txt
index 55bfc014..aeaf3994 100644
--- a/optional-requirements.txt
+++ b/optional-requirements.txt
@@ -1,3 +1,4 @@
 cryptg
 pysocks
 hachoir3
+pillow
diff --git a/telethon/client/uploads.py b/telethon/client/uploads.py
index 57144add..91ce0279 100644
--- a/telethon/client/uploads.py
+++ b/telethon/client/uploads.py
@@ -31,6 +31,7 @@ class _CacheType:
 
 
 def _resize_photo_if_needed(file, is_image, width=1280, height=1280):
+    # https://github.com/telegramdesktop/tdesktop/blob/12905f0dcb9d513378e7db11989455a1b764ef75/Telegram/SourceFiles/boxes/photo_crop_box.cpp#L254
     if (not is_image
             or PIL is None
             or (isinstance(file, io.IOBase) and not file.seekable())):
@@ -164,6 +165,11 @@ class UploadMethods(ButtonMethods, MessageParseMethods, UserMethods):
             If the ``hachoir3`` package (``hachoir`` module) is installed,
             it will be used to determine metadata from audio and video files.
 
+            If the `pillow` package is installed and you are sending a photo,
+            it will be resized to fit within the maximum dimensions allowed
+            by Telegram to avoid ``errors.PhotoInvalidDimensionsError``. This
+            cannot be done if you are sending :tl:`InputFile`, however.
+
         Returns:
             The `telethon.tl.custom.message.Message` (or messages) containing
             the sent file, or messages if a list of them was passed.
diff --git a/telethon_generator/data/errors.csv b/telethon_generator/data/errors.csv
index 61669f8c..6ccd4667 100644
--- a/telethon_generator/data/errors.csv
+++ b/telethon_generator/data/errors.csv
@@ -171,7 +171,7 @@ PHOTO_CONTENT_URL_EMPTY,400,The content from the URL used as a photo appears to
 PHOTO_CROP_SIZE_SMALL,400,Photo is too small
 PHOTO_EXT_INVALID,400,The extension of the photo is invalid
 PHOTO_INVALID,400,Photo invalid
-PHOTO_INVALID_DIMENSIONS,400,The photo dimensions are invalid
+PHOTO_INVALID_DIMENSIONS,400,The photo dimensions are invalid (hint: `pip install pillow` for `send_file` to resize images)
 PHOTO_SAVE_FILE_INVALID,400,The photo you tried to send cannot be saved by Telegram. A reason may be that it exceeds 10MB. Try resizing it locally
 PHOTO_THUMB_URL_EMPTY,400,The URL used as a thumbnail appears to be empty or has caused another HTTP error
 PIN_RESTRICTED,400,You can't pin messages in private chats with other people