diff --git a/src/iterators/exercise.md b/src/iterators/exercise.md
index 55bb176bf940..9594f4f73d3d 100644
--- a/src/iterators/exercise.md
+++ b/src/iterators/exercise.md
@@ -13,7 +13,7 @@ return value.
 
 ```rust
 {{#include exercise.rs:offset_differences}}
-    unimplemented!()
+    todo!()
 }
 
 {{#include exercise.rs:unit-tests}}
diff --git a/src/tuples-and-arrays/exercise.md b/src/tuples-and-arrays/exercise.md
index 1994db2ee6c3..96261f9d388d 100644
--- a/src/tuples-and-arrays/exercise.md
+++ b/src/tuples-and-arrays/exercise.md
@@ -31,7 +31,7 @@ This function only operates on 3x3 matrices.
 #![allow(unused_variables, dead_code)]
 
 {{#include exercise.rs:transpose}}
-    unimplemented!()
+    todo!()
 }
 
 {{#include exercise.rs:tests}}
diff --git a/src/unsafe-rust/exercise.md b/src/unsafe-rust/exercise.md
index 13cf08915637..4fd5b1af5faf 100644
--- a/src/unsafe-rust/exercise.md
+++ b/src/unsafe-rust/exercise.md
@@ -58,17 +58,17 @@ functions and methods:
 {{#include exercise.rs:ffi}}
 
 {{#include exercise.rs:DirectoryIterator}}
-        unimplemented!()
+        todo!()
     }
 }
 
 {{#include exercise.rs:Iterator}}
-        unimplemented!()
+        todo!()
     }
 }
 
 {{#include exercise.rs:Drop}}
-        unimplemented!()
+        todo!()
     }
 }