diff --git a/examples/issue32.rs b/examples/issue32.rs
new file mode 100644
index 0000000..ba34a47
--- /dev/null
+++ b/examples/issue32.rs
@@ -0,0 +1,11 @@
+use memoize::memoize;
+
+#[memoize]
+fn expensive(mut foo: i32) -> i32 {
+    foo += 1;
+    foo
+}
+
+fn main() {
+    expensive(7);
+}
diff --git a/inner/src/lib.rs b/inner/src/lib.rs
index c7d708b..1ce5efe 100644
--- a/inner/src/lib.rs
+++ b/inner/src/lib.rs
@@ -435,7 +435,7 @@ pub fn memoize(attr: TokenStream, item: TokenStream) -> TokenStream {
         #flusher
         #store
 
-        #[allow(unused_variables)]
+        #[allow(unused_variables, unused_mut)]
         #vis #sig {
             #memoizer
         }