filename returns basename when no extension present

lib/paperclip/interpolations.rb

@@ -35,7 +35,7 @@ module Paperclip
 
     # Returns the filename, the same way as ":basename.:extension" would.
     def filename attachment, style_name
-      "#{basename(attachment, style_name)}.#{extension(attachment, style_name)}"
+      (ext = extension(attachment, style_name)).blank? ? basename(attachment, style_name) : "#{basename(attachment, style_name)}.#{ext}"
     end
 
     # Returns the interpolated URL. Will raise an error if the url itself

test/interpolations_test.rb

@@ -110,6 +110,13 @@ class InterpolationsTest < Test::Unit::TestCase
     assert_equal "one.png", Paperclip::Interpolations.filename(attachment, :style)
   end
 
+  should "return the filename as basename when extension is blank" do
+    attachment = mock
+    attachment.stubs(:styles).returns({})
+    attachment.stubs(:original_filename).returns("one")
+    assert_equal "one", Paperclip::Interpolations.filename(attachment, :style)
+  end
+
   should "return the timestamp" do
     now = Time.now
     zone = 'UTC'