diff --git a/compiler/rustc_ast_pretty/src/pp.rs b/compiler/rustc_ast_pretty/src/pp.rs
index dca0515a33033..d9832d560a841 100644
--- a/compiler/rustc_ast_pretty/src/pp.rs
+++ b/compiler/rustc_ast_pretty/src/pp.rs
@@ -380,24 +380,25 @@ impl Printer {
 
     fn check_stack(&mut self, mut k: usize) {
         while let Some(&x) = self.scan_stack.front() {
-            match self.buf[x].token {
+            let mut entry = &mut self.buf[x];
+            match entry.token {
                 Token::Begin(_) => {
                     if k == 0 {
                         break;
                     }
                     self.scan_stack.pop_front().unwrap();
-                    self.buf[x].size += self.right_total;
+                    entry.size += self.right_total;
                     k -= 1;
                 }
                 Token::End => {
                     // paper says + not =, but that makes no sense.
                     self.scan_stack.pop_front().unwrap();
-                    self.buf[x].size = 1;
+                    entry.size = 1;
                     k += 1;
                 }
                 _ => {
                     self.scan_stack.pop_front().unwrap();
-                    self.buf[x].size += self.right_total;
+                    entry.size += self.right_total;
                     if k == 0 {
                         break;
                     }