diff --git a/exercises/17_tests/tests3.rs b/exercises/17_tests/tests3.rs
index 9fc93185..ec994792 100644
--- a/exercises/17_tests/tests3.rs
+++ b/exercises/17_tests/tests3.rs
@@ -29,8 +29,8 @@ mod tests {
         // TODO: This test should check if the rectangle has the size that we
         // pass to its constructor.
         let rect = Rectangle::new(10, 20);
-        assert_eq!(???, 10); // Check width
-        assert_eq!(???, 20); // Check height
+        assert_eq!(todo!(), 10); // Check width
+        assert_eq!(todo!(), 20); // Check height
     }
 
     // TODO: This test should check if the program panics when we try to create
diff --git a/exercises/18_iterators/iterators1.rs b/exercises/18_iterators/iterators1.rs
index 86278a49..ca937ed0 100644
--- a/exercises/18_iterators/iterators1.rs
+++ b/exercises/18_iterators/iterators1.rs
@@ -13,13 +13,13 @@ mod tests {
         let my_fav_fruits = ["banana", "custard apple", "avocado", "peach", "raspberry"];
 
         // TODO: Create an iterator over the array.
-        let mut fav_fruits_iterator = ???;
+        let mut fav_fruits_iterator = todo!();
 
         assert_eq!(fav_fruits_iterator.next(), Some(&"banana"));
-        assert_eq!(fav_fruits_iterator.next(), ???); // TODO: Replace `???`
+        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
         assert_eq!(fav_fruits_iterator.next(), Some(&"avocado"));
-        assert_eq!(fav_fruits_iterator.next(), ???); // TODO: Replace `???`
+        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
         assert_eq!(fav_fruits_iterator.next(), Some(&"raspberry"));
-        assert_eq!(fav_fruits_iterator.next(), ???); // TODO: Replace `???`
+        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
     }
 }