diff --git a/solutions/23_conversions/as_ref_mut.rs b/solutions/23_conversions/as_ref_mut.rs
index 91b12bac..af62e2d8 100644
--- a/solutions/23_conversions/as_ref_mut.rs
+++ b/solutions/23_conversions/as_ref_mut.rs
@@ -15,7 +15,7 @@ fn char_counter<T: AsRef<str>>(arg: T) -> usize {
 // Squares a number using `as_mut()`.
 fn num_sq<T: AsMut<u32>>(arg: &mut T) {
     let arg = arg.as_mut();
-    *arg = *arg * *arg;
+    *arg *= *arg;
 }
 
 fn main() {