diff --git a/src/librustc/back/link.rs b/src/librustc/back/link.rs
index 32cdbfe59fa1..10560d424690 100644
--- a/src/librustc/back/link.rs
+++ b/src/librustc/back/link.rs
@@ -853,7 +853,9 @@ fn link_rlib(sess: Session,
              out_filename: &Path) -> Archive {
     let mut a = Archive::create(sess, out_filename, obj_filename);
 
-    for &(ref l, kind) in sess.cstore.get_used_libraries().iter() {
+    let used_libraries = sess.cstore.get_used_libraries();
+    let used_libraries = used_libraries.borrow();
+    for &(ref l, kind) in used_libraries.get().iter() {
         match kind {
             cstore::NativeStatic => {
                 a.add_native_library(l.as_slice());
@@ -1116,7 +1118,9 @@ fn add_local_native_libraries(args: &mut ~[~str], sess: Session) {
         args.push("-L" + path.as_str().unwrap().to_owned());
     }
 
-    for &(ref l, kind) in sess.cstore.get_used_libraries().iter() {
+    let used_libraries = sess.cstore.get_used_libraries();
+    let used_libraries = used_libraries.borrow();
+    for &(ref l, kind) in used_libraries.get().iter() {
         match kind {
             cstore::NativeUnknown | cstore::NativeStatic => {
                 args.push("-l" + *l);
diff --git a/src/librustc/metadata/cstore.rs b/src/librustc/metadata/cstore.rs
index adf25219acaf..5e4c1901f1e5 100644
--- a/src/librustc/metadata/cstore.rs
+++ b/src/librustc/metadata/cstore.rs
@@ -64,7 +64,7 @@ pub struct CStore {
     priv metas: RefCell<HashMap<ast::CrateNum, @crate_metadata>>,
     priv extern_mod_crate_map: RefCell<extern_mod_crate_map>,
     priv used_crate_sources: RefCell<~[CrateSource]>,
-    priv used_libraries: ~[(~str, NativeLibaryKind)],
+    priv used_libraries: RefCell<~[(~str, NativeLibaryKind)]>,
     priv used_link_args: ~[~str],
     intr: @ident_interner
 }
@@ -78,7 +78,7 @@ impl CStore {
             metas: RefCell::new(HashMap::new()),
             extern_mod_crate_map: RefCell::new(HashMap::new()),
             used_crate_sources: RefCell::new(~[]),
-            used_libraries: ~[],
+            used_libraries: RefCell::new(~[]),
             used_link_args: ~[],
             intr: intr
         }
@@ -137,15 +137,17 @@ impl CStore {
 
     pub fn add_used_library(&mut self, lib: ~str, kind: NativeLibaryKind) -> bool {
         assert!(!lib.is_empty());
-        if self.used_libraries.iter().any(|&(ref x, _)| x == &lib) {
+        let mut used_libraries = self.used_libraries.borrow_mut();
+        if used_libraries.get().iter().any(|&(ref x, _)| x == &lib) {
             return false;
         }
-        self.used_libraries.push((lib, kind));
+        used_libraries.get().push((lib, kind));
         true
     }
 
-    pub fn get_used_libraries<'a>(&'a self) -> &'a [(~str, NativeLibaryKind)] {
-        self.used_libraries.as_slice()
+    pub fn get_used_libraries<'a>(&'a self)
+                              -> &'a RefCell<~[(~str, NativeLibaryKind)]> {
+        &self.used_libraries
     }
 
     pub fn add_used_link_args(&mut self, args: &str) {
diff --git a/src/librustc/metadata/encoder.rs b/src/librustc/metadata/encoder.rs
index 214dc41bf2db..6e4e221fd7ab 100644
--- a/src/librustc/metadata/encoder.rs
+++ b/src/librustc/metadata/encoder.rs
@@ -1611,7 +1611,9 @@ fn encode_lang_items(ecx: &EncodeContext, ebml_w: &mut writer::Encoder) {
 fn encode_native_libraries(ecx: &EncodeContext, ebml_w: &mut writer::Encoder) {
     ebml_w.start_tag(tag_native_libraries);
 
-    for &(ref lib, kind) in ecx.cstore.get_used_libraries().iter() {
+    let used_libraries = ecx.tcx.sess.cstore.get_used_libraries();
+    let used_libraries = used_libraries.borrow();
+    for &(ref lib, kind) in used_libraries.get().iter() {
         match kind {
             cstore::NativeStatic => {} // these libraries are not propagated
             cstore::NativeFramework | cstore::NativeUnknown => {