diff --git a/src/exercises/duration.md b/src/exercises/duration.md
index 1c62826..c3708ae 100644
--- a/src/exercises/duration.md
+++ b/src/exercises/duration.md
@@ -4,12 +4,12 @@ Define `FIVE_SECONDS` as `const`:
 
 ```rust
 # use std::time::Duration;
-# const fn unwrap_time(d: Option<Duration>) -> Duration { match d { Some(d) => d, None => panic!() } }
+# const fn unwrap<T: Copy>(o: Option<T>) -> T { match o { Some(t) => t, None => panic!() } }
 const TWO_SECONDS: Duration = Duration::from_secs(2);
 # /*
 const FIVE_SECONDS: Duration = TWO_SECONDS + Duration::from_secs(3);
 # */
-# const FIVE_SECONDS: Duration = unwrap_time(TWO_SECONDS.checked_add(Duration::from_secs(3)));
+# const FIVE_SECONDS: Duration = unwrap(TWO_SECONDS.checked_add(Duration::from_secs(3)));
 assert_eq!(FIVE_SECONDS, Duration::from_secs(5));
 ```