If file extension is unknown, send_file will always fall back to application/octet-stream rather than complaining. Fixes #127.

lib/sinatra/base.rb

@@ -140,7 +140,8 @@ module Sinatra
     # Set the Content-Type of the response body given a media type or file
     # extension.
     def content_type(type, params={})
-      mime_type = mime_type(type)
+      default = params.delete :default
+      mime_type = mime_type(type) || default
       fail "Unknown media type: %p" % type if mime_type.nil?
       mime_type = mime_type.dup
       unless params.include? :charset or settings.add_charset.all? { |p| not p === mime_type }
@@ -165,10 +166,8 @@ module Sinatra
       stat = File.stat(path)
       last_modified stat.mtime
 
-      content_type opts[:type] ||
-        File.extname(path) ||
-        response['Content-Type'] ||
-        'application/octet-stream'
+      content_type opts[:type] || File.extname(path),
+        :default => response['Content-Type'] || 'application/octet-stream'
 
       if opts[:disposition] == 'attachment' || opts[:filename]
         attachment opts[:filename] || path

test/helpers_test.rb

@@ -446,6 +446,14 @@ class HelpersTest < Test::Unit::TestCase
       get '/file.txt'
       assert_equal 'attachment; filename="foo.txt"', response['Content-Disposition']
     end
+
+    it "is able to send files with unkown mime type" do
+      @file = File.dirname(__FILE__) + '/file.foobar'
+      File.open(@file, 'wb') { |io| io.write('Hello World') }
+      send_file_app
+      get '/file.txt'
+      assert_equal 'application/octet-stream', response['Content-Type']
+    end
   end
 
   describe 'cache_control' do