diff --git a/README.md b/README.md
index f5ef301..f1f47fc 100644
--- a/README.md
+++ b/README.md
@@ -24,6 +24,17 @@ Place the file `freedesktop.org.xml` in an appropriate location, and then set th
 `FREEDESKTOP_MIME_TYPES_PATH` to that path. Once that has been done the gem should install successfully. Please
 note that the gem will depend upon the file remaining in that location at run time.
 
+For Windows
+===============
+
+This was tested in Ruby installed via Ruby Installer, but should work for other methods too.
+
+1. Download 7-Zip from https://www.7-zip.org/download.html
+2. Download the package from https://packages.debian.org/sid/amd64/shared-mime-info/download
+3. Unzip the file in `data.tar\.\usr\share\mime\packages\freedesktop.org.xml` somewhere, for the purpose of this tutorial assuming C:\shared-mime-info
+4. In command line, export environment variable: `set FREEDESKTOP_MIME_TYPES_PATH=C:\shared-mime-info\freedesktop.org.xml`
+5. Install the gem via `bundle install` or `gem install mimemagic`
+
 Usage
 =====
 
diff --git a/ext/mimemagic/Rakefile b/ext/mimemagic/Rakefile
index f0474bf..a4e39d2 100644
--- a/ext/mimemagic/Rakefile
+++ b/ext/mimemagic/Rakefile
@@ -24,7 +24,7 @@ end
 desc "Build a file pointing at the database"
 task :default do
   mime_database_path = locate_mime_database
-  target_dir = "#{ENV.fetch("RUBYARCHDIR", "../lib")}/mimemagic"
+  target_dir = File.join(ENV.fetch("RUBYARCHDIR", "../lib"), "mimemagic")
   mkdir_p target_dir
 
   open("#{target_dir}/path.rb", "w") do |f|