diff --git a/bypy/windows.conf b/bypy/windows.conf
index 6972c2aeb3..f876466f55 100644
--- a/bypy/windows.conf
+++ b/bypy/windows.conf
@@ -1,9 +1,10 @@
-# Requires installation of Visual Studio 2017 Community Edition, Git, Python 3.7 and Perl
+# Requires installation of Visual Studio 2017 Community Edition, Git, Ruby, Python 3.7 and Perl
 # git.exe must be in PATH. Must have ~100GB available disk space and 8GB RAM
-# Intall certifi in python 3 with:
+# Install certifi in python 3 with:
 # py.exe -m pip install certifi
 
 vm_name 'calibre-windows-build'
 root 'C:/r'
 python 'py.exe'
 perl 'C:/Strawberry/perl/bin/perl.exe'
+ruby 'C:/Ruby26-x64/bin/ruby.exe'