diff --git a/src/references/solution.md b/src/references/solution.md
index 5517c2d401bc..f7b469b42b6d 100644
--- a/src/references/solution.md
+++ b/src/references/solution.md
@@ -10,4 +10,9 @@
   element. This is because we're iterating using a mutable reference to an
   array, which causes the `for` loop to give mutable references to each element.
 
+- It is also possible to take slice references here, e.g.,
+  `fn
+  magnitude(vector: &[f64]) -> f64`. This makes the function more general,
+  at the cost of a runtime length check.
+
 </details>