diff --git a/example/mu/example.dtx b/example/mu/example.dtx
index fc53e1be8d3c0d2a1a0949391f26c2303a7c65a1..9ba741c80ec9b7a57f99bd606dfc4fc2e4793793 100644
--- a/example/mu/example.dtx
+++ b/example/mu/example.dtx
@@ -812,7 +812,7 @@ fac() {
 }
 ``````````````
 
-~~~~~~ Ruby
+~~~~~~ ruby
 # Here's a way to empty an array.
 joe = [ 'eggs.', 'some', 'break', 'to', 'Have' ]
 print(joe.pop, " ") while joe.size > 0