diff --git a/serde_derive/src/de.rs b/serde_derive/src/de.rs
index c9154321..a5d6bd4d 100644
--- a/serde_derive/src/de.rs
+++ b/serde_derive/src/de.rs
@@ -6,7 +6,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use syn::{self, Ident, Member};
+use syn::{self, Ident, Index, Member};
 use syn::punctuated::Punctuated;
 use quote::{ToTokens, Tokens};
 use proc_macro2::{Literal, Span, Term};
@@ -624,7 +624,10 @@ fn deserialize_seq_in_place(
             let field_name = field
                 .ident
                 .map(Member::Named)
-                .unwrap_or_else(|| Member::Unnamed(field_index.into()));
+                .unwrap_or_else(|| Member::Unnamed(Index {
+                    index: field_index as u32,
+                    span: Span::call_site(),
+                }));
 
             if field.attrs.skip_deserializing() {
                 let default = Expr(expr_is_missing(field, cattrs));
@@ -2314,7 +2317,10 @@ fn wrap_deserialize_variant_with(
     let (wrapper, wrapper_ty) =
         wrap_deserialize_with(params, &quote!((#(#field_tys),*)), deserialize_with);
 
-    let field_access = (0..variant.fields.len()).map(|n| Member::Unnamed(n.into()));
+    let field_access = (0..variant.fields.len()).map(|n| Member::Unnamed(Index {
+        index: n as u32,
+        span: Span::call_site(),
+    }));
     let unwrap_fn = match variant.style {
         Style::Struct => {
             let field_idents = variant
diff --git a/serde_derive/src/ser.rs b/serde_derive/src/ser.rs
index 32a6b1d4..5f190551 100644
--- a/serde_derive/src/ser.rs
+++ b/serde_derive/src/ser.rs
@@ -6,7 +6,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use syn::{self, Ident, Member};
+use syn::{self, Ident, Index, Member};
 use quote::Tokens;
 use proc_macro2::Span;
 
@@ -202,7 +202,10 @@ fn serialize_newtype_struct(
 ) -> Fragment {
     let type_name = cattrs.name().serialize_name();
 
-    let mut field_expr = get_member(params, field, &Member::Unnamed(0.into()));
+    let mut field_expr = get_member(params, field, &Member::Unnamed(Index {
+        index: 0,
+        span: Span::call_site(),
+    }));
     if let Some(path) = field.attrs.serialize_with() {
         field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
     }
@@ -817,7 +820,10 @@ fn serialize_tuple_struct_visitor(
                 let id = Ident::new(&format!("__field{}", i), Span::def_site());
                 quote!(#id)
             } else {
-                get_member(params, field, &Member::Unnamed(i.into()))
+                get_member(params, field, &Member::Unnamed(Index {
+                    index: i as u32,
+                    span: Span::call_site(),
+                }))
             };
 
             let skip = field
@@ -940,7 +946,10 @@ fn wrap_serialize_with(
     };
     let (wrapper_impl_generics, wrapper_ty_generics, _) = wrapper_generics.split_for_impl();
 
-    let field_access = (0..field_exprs.len()).map(|n| Member::Unnamed(n.into()));
+    let field_access = (0..field_exprs.len()).map(|n| Member::Unnamed(Index {
+        index: n as u32,
+        span: Span::call_site(),
+    }));
 
     quote!({
         struct __SerializeWith #wrapper_impl_generics #where_clause {
diff --git a/test_suite/Cargo.toml b/test_suite/Cargo.toml
index 50e10e36..23a9fd79 100644
--- a/test_suite/Cargo.toml
+++ b/test_suite/Cargo.toml
@@ -9,6 +9,7 @@ unstable = ["serde/unstable", "compiletest_rs"]
 
 [dev-dependencies]
 fnv = "1.0"
+proc-macro2 = "0.2"
 rustc-serialize = "0.3.16"
 serde = { path = "../serde", features = ["rc"] }
 serde_derive = { path = "../serde_derive", features = ["deserialize_in_place"] }