diff --git a/src/librustc/ich/impls_syntax.rs b/src/librustc/ich/impls_syntax.rs
index 70ec72d..de56718 100644
--- a/src/librustc/ich/impls_syntax.rs
+++ b/src/librustc/ich/impls_syntax.rs
@@ -258,7 +258,7 @@
             tokenstream::TokenTree::Delimited(span, delim, ref tts) => {
                 span.hash_stable(hcx, hasher);
                 std_hash::Hash::hash(&delim, hasher);
-                for sub_tt in tts.stream().trees() {
+                for sub_tt in tts.trees() {
                     sub_tt.hash_stable(hcx, hasher);
                 }
             }
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index f895542..f6c381f 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -1474,7 +1474,7 @@
                     _ => {},
                 }
                 TokenTree::Delimited(_, _, tts) => {
-                    self.check_tokens(cx, tts.stream())
+                    self.check_tokens(cx, tts)
                 },
             }
         }
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 99ab9fb..bbcaaac 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -15,7 +15,7 @@
 use source_map::{dummy_spanned, respan, Spanned};
 use symbol::{keywords, Symbol};
 use syntax_pos::{Span, DUMMY_SP};
-use tokenstream::{ThinTokenStream, TokenStream};
+use tokenstream::TokenStream;
 use ThinVec;
 
 use rustc_data_structures::fx::FxHashSet;
@@ -1216,7 +1216,7 @@
 pub struct Mac_ {
     pub path: Path,
     pub delim: MacDelimiter,
-    pub tts: ThinTokenStream,
+    pub tts: TokenStream,
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Debug)]
@@ -1228,13 +1228,13 @@
 
 impl Mac_ {
     pub fn stream(&self) -> TokenStream {
-        self.tts.stream()
+        self.tts.clone()
     }
 }
 
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct MacroDef {
-    pub tokens: ThinTokenStream,
+    pub tokens: TokenStream,
     pub legacy: bool,
 }
 
diff --git a/src/libsyntax/attr/mod.rs b/src/libsyntax/attr/mod.rs
index f83c1ec..f6d7590 100644
--- a/src/libsyntax/attr/mod.rs
+++ b/src/libsyntax/attr/mod.rs
@@ -570,7 +570,7 @@
             }
             Some(TokenTree::Delimited(_, delim, ref tts)) if delim == token::Paren => {
                 tokens.next();
-                tts.stream()
+                tts.clone()
             }
             _ => return Some(MetaItemKind::Word),
         };
diff --git a/src/libsyntax/ext/quote.rs b/src/libsyntax/ext/quote.rs
index c312414..c01e7f5 100644
--- a/src/libsyntax/ext/quote.rs
+++ b/src/libsyntax/ext/quote.rs
@@ -748,7 +748,7 @@
         },
         TokenTree::Delimited(span, delim, ref tts) => {
             let mut stmts = statements_mk_tt(cx, &TokenTree::open_tt(span.open, delim), false);
-            stmts.extend(statements_mk_tts(cx, tts.stream()));
+            stmts.extend(statements_mk_tts(cx, tts.clone()));
             stmts.extend(statements_mk_tt(cx, &TokenTree::close_tt(span.close, delim), false));
             stmts
         }
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index 8ac1038..a4c3b38 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -598,7 +598,7 @@
         TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited(
             DelimSpan::from_pair(fld.new_span(span.open), fld.new_span(span.close)),
             delim,
-            fld.fold_tts(tts.stream()).into(),
+            fld.fold_tts(tts).into(),
         ),
     }
 }
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index ea20553..ddb350f 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -817,7 +817,7 @@
                 )
                 if name_macro_rules.name == "macro_rules"
                 && name_zip.name == "zip" => {
-                    let tts = &macro_tts.stream().trees().collect::<Vec<_>>();
+                    let tts = &macro_tts.trees().collect::<Vec<_>>();
                     match (tts.len(), tts.get(0), tts.get(1), tts.get(2)) {
                         (
                             3,
@@ -826,7 +826,7 @@
                             Some(&TokenTree::Delimited(_, second_delim, ref second_tts)),
                         )
                         if macro_delim == token::Paren => {
-                            let tts = &first_tts.stream().trees().collect::<Vec<_>>();
+                            let tts = &first_tts.trees().collect::<Vec<_>>();
                             match (tts.len(), tts.get(0), tts.get(1)) {
                                 (
                                     2,
@@ -836,7 +836,7 @@
                                 if first_delim == token::Paren && ident.name == "a" => {},
                                 _ => panic!("value 3: {:?} {:?}", first_delim, first_tts),
                             }
-                            let tts = &second_tts.stream().trees().collect::<Vec<_>>();
+                            let tts = &second_tts.trees().collect::<Vec<_>>();
                             match (tts.len(), tts.get(0), tts.get(1)) {
                                 (
                                     2,
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 5b430d1..bdbca30 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -46,7 +46,7 @@
 use ptr::P;
 use parse::PResult;
 use ThinVec;
-use tokenstream::{self, DelimSpan, ThinTokenStream, TokenTree, TokenStream};
+use tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
 use symbol::{Symbol, keywords};
 
 use std::borrow::Cow;
@@ -280,17 +280,17 @@
 /// on the parser.
 #[derive(Clone)]
 enum LastToken {
-    Collecting(Vec<TokenStream>),
-    Was(Option<TokenStream>),
+    Collecting(Vec<TreeAndJoint>),
+    Was(Option<TreeAndJoint>),
 }
 
 impl TokenCursorFrame {
-    fn new(sp: DelimSpan, delim: DelimToken, tts: &ThinTokenStream) -> Self {
+    fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
         TokenCursorFrame {
             delim: delim,
             span: sp,
             open_delim: delim == token::NoDelim,
-            tree_cursor: tts.stream().into_trees(),
+            tree_cursor: tts.clone().into_trees(),
             close_delim: delim == token::NoDelim,
             last_token: LastToken::Was(None),
         }
@@ -2330,7 +2330,7 @@
         })
     }
 
-    fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, ThinTokenStream)> {
+    fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
         let delim = match self.token {
             token::OpenDelim(delim) => delim,
             _ => {
@@ -2350,7 +2350,7 @@
             token::Brace => MacDelimiter::Brace,
             token::NoDelim => self.bug("unexpected no delimiter"),
         };
-        Ok((delim, tts.stream().into()))
+        Ok((delim, tts.into()))
     }
 
     /// At the bottom (top?) of the precedence hierarchy,
@@ -4641,7 +4641,7 @@
                 let ident = self.parse_ident()?;
                 let tokens = if self.check(&token::OpenDelim(token::Brace)) {
                     match self.parse_token_tree() {
-                        TokenTree::Delimited(_, _, tts) => tts.stream(),
+                        TokenTree::Delimited(_, _, tts) => tts,
                         _ => unreachable!(),
                     }
                 } else if self.check(&token::OpenDelim(token::Paren)) {
@@ -7757,7 +7757,7 @@
             &mut self.token_cursor.stack[prev].last_token
         };
 
-        // Pull our the toekns that we've collected from the call to `f` above
+        // Pull out the tokens that we've collected from the call to `f` above.
         let mut collected_tokens = match *last_token {
             LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
             LastToken::Was(_) => panic!("our vector went away?"),
@@ -7776,10 +7776,9 @@
         // call. In that case we need to record all the tokens we collected in
         // our parent list as well. To do that we push a clone of our stream
         // onto the previous list.
-        let stream = collected_tokens.into_iter().collect::<TokenStream>();
         match prev_collecting {
             Some(mut list) => {
-                list.push(stream.clone());
+                list.extend(collected_tokens.iter().cloned());
                 list.extend(extra_token);
                 *last_token = LastToken::Collecting(list);
             }
@@ -7788,7 +7787,7 @@
             }
         }
 
-        Ok((ret?, stream))
+        Ok((ret?, TokenStream::new(collected_tokens)))
     }
 
     pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 2ad3d3a..c535940 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -807,7 +807,7 @@
             TokenTree::Delimited(_, delim, tts) => {
                 self.writer().word(token_to_string(&token::OpenDelim(delim)))?;
                 self.writer().space()?;
-                self.print_tts(tts.stream())?;
+                self.print_tts(tts)?;
                 self.writer().space()?;
                 self.writer().word(token_to_string(&token::CloseDelim(delim)))
             },
diff --git a/src/libsyntax/tokenstream.rs b/src/libsyntax/tokenstream.rs
index fb72ef9..f5d2d6f 100644
--- a/src/libsyntax/tokenstream.rs
+++ b/src/libsyntax/tokenstream.rs
@@ -41,7 +41,7 @@
     /// A single token
     Token(Span, token::Token),
     /// A delimited sequence of token trees
-    Delimited(DelimSpan, DelimToken, ThinTokenStream),
+    Delimited(DelimSpan, DelimToken, TokenStream),
 }
 
 impl TokenTree {
@@ -62,8 +62,7 @@
             (&TokenTree::Token(_, ref tk), &TokenTree::Token(_, ref tk2)) => tk == tk2,
             (&TokenTree::Delimited(_, delim, ref tts),
              &TokenTree::Delimited(_, delim2, ref tts2)) => {
-                delim == delim2 &&
-                tts.stream().eq_unspanned(&tts2.stream())
+                delim == delim2 && tts.eq_unspanned(&tts2)
             }
             (_, _) => false,
         }
@@ -81,8 +80,7 @@
             }
             (&TokenTree::Delimited(_, delim, ref tts),
              &TokenTree::Delimited(_, delim2, ref tts2)) => {
-                delim == delim2 &&
-                tts.stream().probably_equal_for_proc_macro(&tts2.stream())
+                delim == delim2 && tts.probably_equal_for_proc_macro(&tts2)
             }
             (_, _) => false,
         }
@@ -113,7 +111,7 @@
     }
 
     pub fn joint(self) -> TokenStream {
-        TokenStream::Tree(self, Joint)
+        TokenStream::new(vec![(self, Joint)])
     }
 
     /// Returns the opening delimiter as a token tree.
@@ -143,18 +141,19 @@
 /// The goal is for procedural macros to work with `TokenStream`s and `TokenTree`s
 /// instead of a representation of the abstract syntax tree.
 /// Today's `TokenTree`s can still contain AST via `Token::Interpolated` for back-compat.
+///
+/// The use of `Option` is an optimization that avoids the need for an
+/// allocation when the stream is empty. However, it is not guaranteed that an
+/// empty stream is represented with `None`; it may be represented as a `Some`
+/// around an empty `Vec`.
 #[derive(Clone, Debug)]
-pub enum TokenStream {
-    Empty,
-    Tree(TokenTree, IsJoint),
-    Stream(Lrc<Vec<TreeAndJoint>>),
-}
+pub struct TokenStream(Option<Lrc<Vec<TreeAndJoint>>>);
 
 pub type TreeAndJoint = (TokenTree, IsJoint);
 
 // `TokenStream` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_TOKEN_STREAM: mem::size_of::<TokenStream>() == 32);
+static_assert!(MEM_SIZE_OF_TOKEN_STREAM: mem::size_of::<TokenStream>() == 8);
 
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum IsJoint {
@@ -169,7 +168,7 @@
     /// separating the two arguments with a comma for diagnostic suggestions.
     pub(crate) fn add_comma(&self) -> Option<(TokenStream, Span)> {
         // Used to suggest if a user writes `foo!(a b);`
-        if let TokenStream::Stream(ref stream) = self {
+        if let Some(ref stream) = self.0 {
             let mut suggestion = None;
             let mut iter = stream.iter().enumerate().peekable();
             while let Some((pos, ts)) = iter.next() {
@@ -201,7 +200,7 @@
 
 impl From<TokenTree> for TokenStream {
     fn from(tree: TokenTree) -> TokenStream {
-        TokenStream::Tree(tree, NonJoint)
+        TokenStream::new(vec![(tree, NonJoint)])
     }
 }
 
@@ -233,7 +232,7 @@
 
 impl TokenStream {
     pub fn len(&self) -> usize {
-        if let TokenStream::Stream(ref slice) = self {
+        if let Some(ref slice) = self.0 {
             slice.len()
         } else {
             0
@@ -241,13 +240,13 @@
     }
 
     pub fn empty() -> TokenStream {
-        TokenStream::Empty
+        TokenStream(None)
     }
 
     pub fn is_empty(&self) -> bool {
-        match self {
-            TokenStream::Empty => true,
-            _ => false,
+        match self.0 {
+            None => true,
+            Some(ref stream) => stream.is_empty(),
         }
     }
 
@@ -258,10 +257,9 @@
             _ => {
                 let mut vec = vec![];
                 for stream in streams {
-                    match stream {
-                        TokenStream::Empty => {},
-                        TokenStream::Tree(tree, is_joint) => vec.push((tree, is_joint)),
-                        TokenStream::Stream(stream2) => vec.extend(stream2.iter().cloned()),
+                    match stream.0 {
+                        None => {},
+                        Some(stream2) => vec.extend(stream2.iter().cloned()),
                     }
                 }
                 TokenStream::new(vec)
@@ -269,22 +267,16 @@
         }
     }
 
-    pub fn new(mut streams: Vec<TreeAndJoint>) -> TokenStream {
+    pub fn new(streams: Vec<TreeAndJoint>) -> TokenStream {
         match streams.len() {
-            0 => TokenStream::empty(),
-            1 => {
-                let (tree, is_joint) = streams.pop().unwrap();
-                TokenStream::Tree(tree, is_joint)
-            }
-            _ => TokenStream::Stream(Lrc::new(streams)),
+            0 => TokenStream(None),
+            _ => TokenStream(Some(Lrc::new(streams))),
         }
     }
 
     pub fn append_to_tree_and_joint_vec(self, vec: &mut Vec<TreeAndJoint>) {
-        match self {
-            TokenStream::Empty => {}
-            TokenStream::Tree(tree, is_joint) => vec.push((tree, is_joint)),
-            TokenStream::Stream(stream) => vec.extend(stream.iter().cloned()),
+        if let Some(stream) = self.0 {
+            vec.extend(stream.iter().cloned());
         }
     }
 
@@ -349,51 +341,36 @@
     }
 
     pub fn map_enumerated<F: FnMut(usize, TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream {
-        match self {
-            TokenStream::Empty => TokenStream::Empty,
-            TokenStream::Tree(tree, is_joint) => TokenStream::Tree(f(0, tree), is_joint),
-            TokenStream::Stream(stream) => TokenStream::Stream(Lrc::new(
+        TokenStream(self.0.map(|stream| {
+            Lrc::new(
                 stream
                     .iter()
                     .enumerate()
                     .map(|(i, (tree, is_joint))| (f(i, tree.clone()), *is_joint))
-                    .collect()
-            )),
-        }
+                    .collect())
+        }))
     }
 
     pub fn map<F: FnMut(TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream {
-        match self {
-            TokenStream::Empty => TokenStream::Empty,
-            TokenStream::Tree(tree, is_joint) => TokenStream::Tree(f(tree), is_joint),
-            TokenStream::Stream(stream) => TokenStream::Stream(Lrc::new(
+        TokenStream(self.0.map(|stream| {
+            Lrc::new(
                 stream
                     .iter()
                     .map(|(tree, is_joint)| (f(tree.clone()), *is_joint))
-                    .collect()
-            )),
-        }
+                    .collect())
+        }))
     }
 
-    fn first_tree_and_joint(&self) -> Option<(TokenTree, IsJoint)> {
-        match self {
-            TokenStream::Empty => None,
-            TokenStream::Tree(ref tree, is_joint) => Some((tree.clone(), *is_joint)),
-            TokenStream::Stream(ref stream) => Some(stream.first().unwrap().clone())
-        }
+    fn first_tree_and_joint(&self) -> Option<TreeAndJoint> {
+        self.0.as_ref().map(|stream| {
+            stream.first().unwrap().clone()
+        })
     }
 
     fn last_tree_if_joint(&self) -> Option<TokenTree> {
-        match self {
-            TokenStream::Empty => None,
-            TokenStream::Tree(ref tree, is_joint) => {
-                if *is_joint == Joint {
-                    Some(tree.clone())
-                } else {
-                    None
-                }
-            }
-            TokenStream::Stream(ref stream) => {
+        match self.0 {
+            None => None,
+            Some(ref stream) => {
                 if let (tree, Joint) = stream.last().unwrap() {
                     Some(tree.clone())
                 } else {
@@ -422,7 +399,7 @@
                     self.push_all_but_last_tree(&last_stream);
                     let glued_span = last_span.to(span);
                     let glued_tt = TokenTree::Token(glued_span, glued_tok);
-                    let glued_tokenstream = TokenStream::Tree(glued_tt, is_joint);
+                    let glued_tokenstream = TokenStream::new(vec![(glued_tt, is_joint)]);
                     self.0.push(glued_tokenstream);
                     self.push_all_but_first_tree(&stream);
                     return
@@ -437,23 +414,21 @@
     }
 
     fn push_all_but_last_tree(&mut self, stream: &TokenStream) {
-        if let TokenStream::Stream(ref streams) = stream {
+        if let Some(ref streams) = stream.0 {
             let len = streams.len();
             match len {
                 1 => {}
-                2 => self.0.push(TokenStream::Tree(streams[0].0.clone(), streams[0].1)),
-                _ => self.0.push(TokenStream::Stream(Lrc::new(streams[0 .. len - 1].to_vec()))),
+                _ => self.0.push(TokenStream(Some(Lrc::new(streams[0 .. len - 1].to_vec())))),
             }
         }
     }
 
     fn push_all_but_first_tree(&mut self, stream: &TokenStream) {
-        if let TokenStream::Stream(ref streams) = stream {
+        if let Some(ref streams) = stream.0 {
             let len = streams.len();
             match len {
                 1 => {}
-                2 => self.0.push(TokenStream::Tree(streams[1].0.clone(), streams[1].1)),
-                _ => self.0.push(TokenStream::Stream(Lrc::new(streams[1 .. len].to_vec()))),
+                _ => self.0.push(TokenStream(Some(Lrc::new(streams[1 .. len].to_vec())))),
             }
         }
     }
@@ -479,17 +454,9 @@
     }
 
     pub fn next_with_joint(&mut self) -> Option<TreeAndJoint> {
-        match self.stream {
-            TokenStream::Empty => None,
-            TokenStream::Tree(ref tree, ref is_joint) => {
-                if self.index == 0 {
-                    self.index = 1;
-                    Some((tree.clone(), *is_joint))
-                } else {
-                    None
-                }
-            }
-            TokenStream::Stream(ref stream) => {
+        match self.stream.0 {
+            None => None,
+            Some(ref stream) => {
                 if self.index < stream.len() {
                     self.index += 1;
                     Some(stream[self.index - 1].clone())
@@ -505,63 +472,19 @@
             return;
         }
         let index = self.index;
-        let stream = mem::replace(&mut self.stream, TokenStream::Empty);
+        let stream = mem::replace(&mut self.stream, TokenStream(None));
         *self = TokenStream::from_streams(vec![stream, new_stream]).into_trees();
         self.index = index;
     }
 
     pub fn look_ahead(&self, n: usize) -> Option<TokenTree> {
-        match self.stream {
-            TokenStream::Empty => None,
-            TokenStream::Tree(ref tree, _) => {
-                if n == 0 && self.index == 0 {
-                    Some(tree.clone())
-                } else {
-                    None
-                }
-            }
-            TokenStream::Stream(ref stream) =>
-                stream[self.index ..].get(n).map(|(tree, _)| tree.clone()),
+        match self.stream.0 {
+            None => None,
+            Some(ref stream) => stream[self.index ..].get(n).map(|(tree, _)| tree.clone()),
         }
     }
 }
 
-/// The `TokenStream` type is large enough to represent a single `TokenTree` without allocation.
-/// `ThinTokenStream` is smaller, but needs to allocate to represent a single `TokenTree`.
-/// We must use `ThinTokenStream` in `TokenTree::Delimited` to avoid infinite size due to recursion.
-#[derive(Debug, Clone)]
-pub struct ThinTokenStream(Option<Lrc<Vec<TreeAndJoint>>>);
-
-impl ThinTokenStream {
-    pub fn stream(&self) -> TokenStream {
-        self.clone().into()
-    }
-}
-
-impl From<TokenStream> for ThinTokenStream {
-    fn from(stream: TokenStream) -> ThinTokenStream {
-        ThinTokenStream(match stream {
-            TokenStream::Empty => None,
-            TokenStream::Tree(tree, is_joint) => Some(Lrc::new(vec![(tree, is_joint)])),
-            TokenStream::Stream(stream) => Some(stream),
-        })
-    }
-}
-
-impl From<ThinTokenStream> for TokenStream {
-    fn from(stream: ThinTokenStream) -> TokenStream {
-        stream.0.map(TokenStream::Stream).unwrap_or_else(TokenStream::empty)
-    }
-}
-
-impl Eq for ThinTokenStream {}
-
-impl PartialEq<ThinTokenStream> for ThinTokenStream {
-    fn eq(&self, other: &ThinTokenStream) -> bool {
-        TokenStream::from(self.clone()) == TokenStream::from(other.clone())
-    }
-}
-
 impl fmt::Display for TokenStream {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.write_str(&pprust::tokens_to_string(self.clone()))
@@ -580,18 +503,6 @@
     }
 }
 
-impl Encodable for ThinTokenStream {
-    fn encode<E: Encoder>(&self, encoder: &mut E) -> Result<(), E::Error> {
-        TokenStream::from(self.clone()).encode(encoder)
-    }
-}
-
-impl Decodable for ThinTokenStream {
-    fn decode<D: Decoder>(decoder: &mut D) -> Result<ThinTokenStream, D::Error> {
-        TokenStream::decode(decoder).map(Into::into)
-    }
-}
-
 #[derive(Debug, Copy, Clone, PartialEq, RustcEncodable, RustcDecodable)]
 pub struct DelimSpan {
     pub open: Span,
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 156546b..8cbd47c 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -832,7 +832,7 @@
 pub fn walk_tt<'a, V: Visitor<'a>>(visitor: &mut V, tt: TokenTree) {
     match tt {
         TokenTree::Token(_, tok) => visitor.visit_token(tok),
-        TokenTree::Delimited(_, _, tts) => visitor.visit_tts(tts.stream()),
+        TokenTree::Delimited(_, _, tts) => visitor.visit_tts(tts),
     }
 }
 
diff --git a/src/libsyntax_ext/proc_macro_server.rs b/src/libsyntax_ext/proc_macro_server.rs
index 158cbc7..7de9b93 100644
--- a/src/libsyntax_ext/proc_macro_server.rs
+++ b/src/libsyntax_ext/proc_macro_server.rs
@@ -269,7 +269,7 @@
         };
 
         let tree = tokenstream::TokenTree::Token(span, token);
-        TokenStream::Tree(tree, if joint { Joint } else { NonJoint })
+        TokenStream::new(vec![(tree, if joint { Joint } else { NonJoint })])
     }
 }