diff --git a/app/controllers/attachments_controller.rb b/app/controllers/attachments_controller.rb
index 8e28194a3..4d4485d03 100644
--- a/app/controllers/attachments_controller.rb
+++ b/app/controllers/attachments_controller.rb
@@ -105,7 +105,7 @@ class AttachmentsController < ApplicationController
       return
     end
 
-    @attachment = Attachment.new(:file => request.body)
+    @attachment = Attachment.new(:file => raw_request_body)
     @attachment.author = User.current
     @attachment.filename = params[:filename].presence || Redmine::Utils.random_hex(16)
     @attachment.content_type = params[:content_type].presence
@@ -303,4 +303,14 @@ class AttachmentsController < ApplicationController
   def update_all_params
     params.permit(:attachments => [:filename, :description]).require(:attachments)
   end
+
+  # Get an IO-like object for the request body which is usable to create a new
+  # attachment. We try to avoid having to read the whole body into memory.
+  def raw_request_body
+    if request.body.respond_to?(:size)
+      request.body
+    else
+      request.raw_body
+    end
+  end
 end