diff --git a/serde_derive/src/bound.rs b/serde_derive/src/bound.rs
index 6d7402cb..abca467b 100644
--- a/serde_derive/src/bound.rs
+++ b/serde_derive/src/bound.rs
@@ -50,7 +50,7 @@ pub fn with_where_predicates_from_fields(
         .data
         .all_fields()
         .filter_map(|field| from_field(&field.attrs))
-        .flat_map(|predicates| predicates.to_vec());
+        .flat_map(<[syn::WherePredicate]>::to_vec);
 
     let mut generics = generics.clone();
     generics.make_where_clause().predicates.extend(predicates);
@@ -72,7 +72,7 @@ pub fn with_where_predicates_from_variants(
     let predicates = variants
         .iter()
         .filter_map(|variant| from_variant(&variant.attrs))
-        .flat_map(|predicates| predicates.to_vec());
+        .flat_map(<[syn::WherePredicate]>::to_vec);
 
     let mut generics = generics.clone();
     generics.make_where_clause().predicates.extend(predicates);