diff --git a/src/lib.rs b/src/lib.rs
index 1228bb9..1276fe4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -21,7 +21,7 @@ struct Concrete {
     count: isize,
 }
 
-fn func<A: API>(a: A) {
+fn func<A: API>(a: &mut A) {
     a.reset();
 }