diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index c2e5763237d3c..7d2a1b3c4a4d2 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -73,7 +73,7 @@ fn mk_sp(lo: BytePos, hi: BytePos) -> Span {
 }
 
 impl<'a> StringReader<'a> {
-    fn next_token(&mut self) -> TokenAndSpan where Self: Sized {
+    fn next_token(&mut self) -> TokenAndSpan {
         let res = self.try_next_token();
         self.unwrap_or_abort(res)
     }