diff --git a/app/models/upload.rb b/app/models/upload.rb
index d7fd2f7ae2b..828eacee54a 100644
--- a/app/models/upload.rb
+++ b/app/models/upload.rb
@@ -99,7 +99,7 @@ class Upload < ActiveRecord::Base
   end
 
   def self.is_on_s3?(url)
-    SiteSetting.enable_s3_uploads? && url.start_with?(S3Store.base_url)
+    SiteSetting.enable_s3_uploads? && (url.start_with?(S3Store.base_url) || url.start_with?(S3Store.base_url_old))
   end
 
   def self.get_from_url(url)
diff --git a/lib/s3_store.rb b/lib/s3_store.rb
index 753f8045974..a61d311e2ca 100644
--- a/lib/s3_store.rb
+++ b/lib/s3_store.rb
@@ -16,6 +16,10 @@ module S3Store
     "//s3.amazonaws.com/#{SiteSetting.s3_upload_bucket}"
   end
 
+  def self.base_url_old
+    "//#{SiteSetting.s3_upload_bucket.downcase}.s3.amazonaws.com"
+  end
+
   def self.remove_file(url)
     S3Store.check_missing_site_settings
 
diff --git a/spec/models/upload_spec.rb b/spec/models/upload_spec.rb
index 34df67d3a04..268a52b01c7 100644
--- a/spec/models/upload_spec.rb
+++ b/spec/models/upload_spec.rb
@@ -174,6 +174,24 @@ describe Upload do
 
   end
 
+  context ".is_on_s3?" do
+
+    before do
+      SiteSetting.stubs(:enable_s3_uploads).returns(true)
+      SiteSetting.stubs(:s3_upload_bucket).returns("BuCkEt")
+   end
+
+    it "case-insensitively matches the old subdomain format" do
+      Upload.is_on_s3?("//bucket.s3.amazonaws.com/1337.png").should == true
+    end
+
+    it "case-sensitively matches the new folder format" do
+      Upload.is_on_s3?("//s3.amazonaws.com/BuCkEt/1337.png").should == true
+      Upload.is_on_s3?("//s3.amazonaws.com/bucket/1337.png").should == false
+    end
+
+  end
+
   context ".get_from_url" do
 
     it "works only when the file has been uploaded" do