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compilation.markdown

@@ -71,6 +71,14 @@ Cross compiling using MinGW32:
 ```
 This will prepare and generate a 32-bit package for Windows. Currently we use `i586-mingw32msvc`.
 
+If you want to create an extension supporting both 32- and 64-bit Firefox on Windows the n you need to run this sequence:
+``` shell
+./scripts/build_with_mingw32.sh w32 # Uses i686-w64-mingw32
+make clean
+./scripts/build_with_mingw32.sh w64 # Uses x86_64-w64-mingw32
+make clean
+```
+
 ## Creating Chrome Package
 
 ``` shell