diff --git a/src/lib.rs b/src/lib.rs
index 77ede94..1228bb9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,7 +3,7 @@
 //! error[E0277]: the trait bound `&mut Concrete: API` is not satisfied
 //!   --> src/lib.rs:32:14
 //!    |
-//! 24 | fn func<A: API>(mut a: A) {
+//! 24 | fn func<A: API>(a: A) {
 //!    |            --- required by this bound in `func`
 //! ...
 //! 32 |         func(self);
@@ -21,7 +21,7 @@ struct Concrete {
     count: isize,
 }
 
-fn func<A: API>(mut a: A) {
+fn func<A: API>(a: A) {
     a.reset();
 }