diff --git a/conf.py.sample b/conf.py.sample
index 85ade3a..db9c184 100644
--- a/conf.py.sample
+++ b/conf.py.sample
@@ -23,6 +23,9 @@ config["ALLOWED_EXTENSIONS"] = set(['txt', 'pdf', 'png', 'jpg', 'jpeg', 'gif'])
 config["DELETE_FILES"] = True
 config["TIME"] = 30
 config["CLEAN_INTERVAL"] = 120
+# If possible, make your web server return a 413 instead of using this
+config["CHECK_FILESIZE"] = True
+config["MAX_FILESIZE"] = 1024 * 1024 * 100 # 100 MiB
 
 # Site info displayed to the user
 config["SITE_DATA"] = {
diff --git a/run.py b/run.py
index 5049387..869eb87 100755
--- a/run.py
+++ b/run.py
@@ -79,6 +79,10 @@ def upload_file():
 
     # Only continue if a file that's allowed gets submitted.
     if file and allowed_file(file.filename):
+      if config["CHECK_FILESIZE"]:
+        data = request.files["file"].read()
+        if len(data) >= config["MAX_FILESIZE"]:
+          return error_page("O-o-onii-chan, noo it's too big ~~"), 413
       filename = secure_filename(file.filename)
       while os.path.exists(os.path.join(config["UPLOAD_FOLDER"], filename)):
         filename = str(randint(1000,8999)) + '-' + secure_filename(filename)