diff --git a/lib/paperclip/interpolations.rb b/lib/paperclip/interpolations.rb
index f9a9398a1..935f39078 100644
--- a/lib/paperclip/interpolations.rb
+++ b/lib/paperclip/interpolations.rb
@@ -143,11 +143,7 @@ def hash attachment, style_name
     # Returns the id of the instance in a split path form. e.g. returns
     # 000/001/234 for an id of 1234.
     def id_partition attachment, style_name
-      if (id = attachment.instance.id).is_a?(Integer)
-        ("%09d" % id).scan(/\d{3}/).join("/")
-      else
-        id.scan(/.{3}/).first(3).join("/")
-      end
+      ("%09d" % attachment.instance.id).scan(/\d{3}/).join("/")
     end
 
     # Returns the pluralized form of the attachment name. e.g.
diff --git a/test/interpolations_test.rb b/test/interpolations_test.rb
index 6fb843007..e807543fd 100644
--- a/test/interpolations_test.rb
+++ b/test/interpolations_test.rb
@@ -88,20 +88,13 @@ class InterpolationsTest < Test::Unit::TestCase
     assert_equal 23, Paperclip::Interpolations.id(attachment, :style)
   end
 
-  should "return the partitioned id of the attachment when the id is an integer" do
+  should "return the partitioned id of the attachment" do
     attachment = mock
     attachment.expects(:id).returns(23)
     attachment.expects(:instance).returns(attachment)
     assert_equal "000/000/023", Paperclip::Interpolations.id_partition(attachment, :style)
   end
 
-  should "return the partitioned id of the attachment when the id is a string" do
-    attachment = mock
-    attachment.expects(:id).returns("32fnj23oio2f")
-    attachment.expects(:instance).returns(attachment)
-    assert_equal "32f/nj2/3oi", Paperclip::Interpolations.id_partition(attachment, :style)
-  end
-
   should "return the name of the attachment" do
     attachment = mock
     attachment.expects(:name).returns("file")