diff --git a/src/librustc/session/code_stats.rs b/src/librustc/session/code_stats.rs
index 0f535249b5e2a..5baf0c5948f28 100644
--- a/src/librustc/session/code_stats.rs
+++ b/src/librustc/session/code_stats.rs
@@ -1,6 +1,7 @@
 use rustc_target::abi::{Align, Size};
 use rustc_data_structures::fx::{FxHashSet};
 use std::cmp::{self, Ordering};
+use rustc_data_structures::sync::Lock;
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub struct VariantInfo {
@@ -44,13 +45,13 @@ pub struct TypeSizeInfo {
     pub variants: Vec<VariantInfo>,
 }
 
-#[derive(PartialEq, Eq, Debug, Default)]
+#[derive(Default)]
 pub struct CodeStats {
-    type_sizes: FxHashSet<TypeSizeInfo>,
+    type_sizes: Lock<FxHashSet<TypeSizeInfo>>,
 }
 
 impl CodeStats {
-    pub fn record_type_size<S: ToString>(&mut self,
+    pub fn record_type_size<S: ToString>(&self,
                                          kind: DataTypeKind,
                                          type_desc: S,
                                          align: Align,
@@ -73,11 +74,12 @@ impl CodeStats {
             opt_discr_size: opt_discr_size.map(|s| s.bytes()),
             variants,
         };
-        self.type_sizes.insert(info);
+        self.type_sizes.borrow_mut().insert(info);
     }
 
     pub fn print_type_sizes(&self) {
-        let mut sorted: Vec<_> = self.type_sizes.iter().collect();
+        let type_sizes = self.type_sizes.borrow();
+        let mut sorted: Vec<_> = type_sizes.iter().collect();
 
         // Primary sort: large-to-small.
         // Secondary sort: description (dictionary order)
diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index bab7ab89ce751..920438da0d638 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -124,7 +124,7 @@ pub struct Session {
     pub perf_stats: PerfStats,
 
     /// Data about code being compiled, gathered during compilation.
-    pub code_stats: Lock<CodeStats>,
+    pub code_stats: CodeStats,
 
     /// If `-zfuel=crate=n` is specified, `Some(crate)`.
     optimization_fuel_crate: Option<String>,
diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index 4bf500555f14b..56fa2d6e89dca 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -1614,13 +1614,13 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         // (delay format until we actually need it)
         let record = |kind, packed, opt_discr_size, variants| {
             let type_desc = format!("{:?}", layout.ty);
-            self.tcx.sess.code_stats.borrow_mut().record_type_size(kind,
-                                                                   type_desc,
-                                                                   layout.align.abi,
-                                                                   layout.size,
-                                                                   packed,
-                                                                   opt_discr_size,
-                                                                   variants);
+            self.tcx.sess.code_stats.record_type_size(kind,
+                                                      type_desc,
+                                                      layout.align.abi,
+                                                      layout.size,
+                                                      packed,
+                                                      opt_discr_size,
+                                                      variants);
         };
 
         let adt_def = match layout.ty.kind {
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 7973a804f1a46..294019496e1c5 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -394,7 +394,7 @@ pub fn run_compiler(
         mem::drop(compiler.global_ctxt()?.take());
 
         if sess.opts.debugging_opts.print_type_sizes {
-            sess.code_stats.borrow().print_type_sizes();
+            sess.code_stats.print_type_sizes();
         }
 
         compiler.link()?;