diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index 45aa6f881e8..3d187cfc081 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -665,7 +665,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// reference to the context, to allow formatting values that need it.
     pub fn create_and_enter<F, R>(s: &'tcx Session,
                                   arenas: &'tcx CtxtArenas<'tcx>,
-                                  def_map: RefCell<DefMap>,
+                                  def_map: DefMap,
                                   named_region_map: resolve_lifetime::NamedRegionMap,
                                   map: ast_map::Map<'tcx>,
                                   freevars: FreevarMap,
@@ -693,7 +693,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             item_variance_map: RefCell::new(DepTrackingMap::new(dep_graph.clone())),
             variance_computed: Cell::new(false),
             sess: s,
-            def_map: def_map,
+            def_map: RefCell::new(def_map),
             tables: RefCell::new(Tables::empty()),
             impl_trait_refs: RefCell::new(DepTrackingMap::new(dep_graph.clone())),
             trait_defs: RefCell::new(DepTrackingMap::new(dep_graph.clone())),
diff --git a/src/librustc_driver/driver.rs b/src/librustc_driver/driver.rs
index d6d944fde5f..cbbbd84ec50 100644
--- a/src/librustc_driver/driver.rs
+++ b/src/librustc_driver/driver.rs
@@ -44,7 +44,6 @@ use super::Compilation;
 
 use serialize::json;
 
-use std::cell::RefCell;
 use std::collections::HashMap;
 use std::env;
 use std::ffi::{OsString, OsStr};
@@ -893,7 +892,7 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
     let trait_map = resolutions.trait_map;
     TyCtxt::create_and_enter(sess,
                              arenas,
-                             RefCell::new(resolutions.def_map),
+                             resolutions.def_map,
                              named_region_map,
                              hir_map,
                              resolutions.freevars,
diff --git a/src/librustc_driver/test.rs b/src/librustc_driver/test.rs
index b1df80403c0..6423d94e6f6 100644
--- a/src/librustc_driver/test.rs
+++ b/src/librustc_driver/test.rs
@@ -29,7 +29,6 @@ use rustc_metadata::cstore::CStore;
 use rustc_metadata::creader::read_local_crates;
 use rustc::hir::map as hir_map;
 use rustc::session::{self, config};
-use std::cell::RefCell;
 use std::rc::Rc;
 use syntax::ast;
 use syntax::abi::Abi;
@@ -140,7 +139,7 @@ fn test_env<F>(source_string: &str,
     let index = stability::Index::new(&ast_map);
     TyCtxt::create_and_enter(&sess,
                              &arenas,
-                             RefCell::new(resolutions.def_map),
+                             resolutions.def_map,
                              named_region_map.unwrap(),
                              ast_map,
                              resolutions.freevars,