diff --git a/patterns/builder.md b/patterns/builder.md
index f697889..570043f 100644
--- a/patterns/builder.md
+++ b/patterns/builder.md
@@ -7,7 +7,7 @@ Construct an object with calls to a builder helper.
 
 ## Example
 
-```
+```rust
 struct Foo {
     // Lots of complicated fields.
 }