diff --git a/src/doc/trpl/for-loops.md b/src/doc/trpl/for-loops.md
index 79720a31740e7..2866cee3a1a63 100644
--- a/src/doc/trpl/for-loops.md
+++ b/src/doc/trpl/for-loops.md
@@ -69,6 +69,7 @@ Don't forget to add the parentheses around the range.
 ## On iterators:
 
 ```rust
+# let lines = "hello\nworld".lines();
 for (linenumber, line) in lines.enumerate() {
     println!("{}: {}", linenumber, line);
 }