diff --git a/app/logical/danbooru/http.rb b/app/logical/danbooru/http.rb
index 2508abe86..a0b8944e2 100644
--- a/app/logical/danbooru/http.rb
+++ b/app/logical/danbooru/http.rb
@@ -148,12 +148,12 @@ module Danbooru
         response = get(url)
 
         raise DownloadError, "Downloading #{response.uri} failed with code #{response.status}" if response.status != 200
-        raise FileTooLargeError, response if @max_size && response.content_length.to_i > @max_size
+        raise FileTooLargeError, "File size too large (size: #{response.content_length.to_i.to_formatted_s(:human_size)}; max size: #{@max_size.to_formatted_s(:human_size)})" if @max_size && response.content_length.to_i > @max_size
 
         size = 0
         response.body.each do |chunk|
           size += chunk.size
-          raise FileTooLargeError if @max_size && size > @max_size
+          raise FileTooLargeError, "File size too large (max size: #{@max_size.to_formatted_s(:human_size)})" if @max_size && size > @max_size
           file.write(chunk)
         end
 
diff --git a/app/models/media_asset.rb b/app/models/media_asset.rb
index e9dad1980..79af6f49d 100644
--- a/app/models/media_asset.rb
+++ b/app/models/media_asset.rb
@@ -39,7 +39,7 @@ class MediaAsset < ApplicationRecord
 
   validates :md5, uniqueness: { conditions: -> { where(status: [:processing, :active]) } }
   validates :file_ext, inclusion: { in: %w[jpg png gif mp4 webm swf zip], message: "Not an image or video" }
-  validates :file_size, numericality: { less_than_or_equal_to: Danbooru.config.max_file_size }
+  validates :file_size, numericality: { less_than_or_equal_to: Danbooru.config.max_file_size, message: ->(asset, _) { "too large (size: #{asset.file_size.to_formatted_s(:human_size)}; max size: #{Danbooru.config.max_file_size.to_formatted_s(:human_size)})" } }
   validates :duration, numericality: { less_than_or_equal_to: MAX_VIDEO_DURATION, message: "must be less than #{MAX_VIDEO_DURATION} seconds", allow_nil: true }, on: :create # XXX should allow admins to bypass
   validate :validate_resolution, on: :create
 
diff --git a/test/functional/uploads_controller_test.rb b/test/functional/uploads_controller_test.rb
index 6d26746b7..ea0ece1e9 100644
--- a/test/functional/uploads_controller_test.rb
+++ b/test/functional/uploads_controller_test.rb
@@ -177,18 +177,32 @@ class UploadsControllerTest < ActionDispatch::IntegrationTest
         assert_match("Not an image or video", Upload.last.error)
       end
 
-      should "fail if the file size is too large" do
-        skip "flaky test"
-        Danbooru.config.stubs(:max_file_size).returns(1.kilobyte)
+      context "for a file larger than the file size limit" do
+        setup do
+          skip "flaky test"
+          Danbooru.config.stubs(:max_file_size).returns(1.kilobyte)
+        end
 
-        file = Rack::Test::UploadedFile.new("test/files/test.jpg")
-        post_auth uploads_path(format: :json), @user, params: { upload: { file: file }}
-        perform_enqueued_jobs
+        should "fail for a direct file upload" do
+          create_upload!("test/files/test.jpg", user: @user)
 
-        assert_response 201
-        assert_match("File size must be less than or equal to", Upload.last.error)
+          assert_response 201
+          assert_match("File size too large", Upload.last.error)
+        end
 
-        Danbooru.config.unstub(:max_file_size)
+        should "fail for a source upload with a Content-Length header" do
+          create_upload!("https://nghttp2.org/httpbin/bytes/2000", user: @user)
+
+          assert_response 201
+          assert_match("File size too large", Upload.last.error)
+        end
+
+        should "fail for a source upload without a Content-Length header" do
+          create_upload!("https://nghttp2.org/httpbin/stream-bytes/2000", user: @user)
+
+          assert_response 201
+          assert_match("File size too large", Upload.last.error)
+        end
       end
 
       context "for a corrupted image" do