diff --git a/src/util.rs b/src/util.rs
index 2c42ed16..efdc4278 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -57,7 +57,7 @@ where
 {
     let opt = Option::<String>::deserialize(de)?;
     // TODO: Switch to and remove this attribute `opt.as_deref()` once MSRV is >= 1.40
-    #[allow(clippy::option_as_ref_deref)]
+    #[allow(clippy::option_as_ref_deref, clippy::unknown_clippy_lints)]
     let opt = opt.as_ref().map(String::as_str);
     match opt {
         None | Some("") => Ok(None),