diff --git a/core/lib/src/local/client.rs b/core/lib/src/local/client.rs
index 1d0f7be7..4a6a8320 100644
--- a/core/lib/src/local/client.rs
+++ b/core/lib/src/local/client.rs
@@ -1,4 +1,4 @@
-use std::cell::RefCell;
+use std::sync::RwLock;
 use std::borrow::Cow;
 
 use Rocket;
@@ -53,7 +53,7 @@ use error::LaunchError;
 /// [`post`]: #method.post
 pub struct Client {
     rocket: Rocket,
-    crate cookies: Option<RefCell<CookieJar>>,
+    crate cookies: Option<RwLock<CookieJar>>,
 }
 
 impl Client {
@@ -62,7 +62,7 @@ impl Client {
     /// set to `None`.
     fn _new(rocket: Rocket, tracked: bool) -> Result<Client, LaunchError> {
         let cookies = match tracked {
-            true => Some(RefCell::new(CookieJar::new())),
+            true => Some(RwLock::new(CookieJar::new())),
             false => None
         };
 
@@ -321,3 +321,15 @@ impl Client {
         LocalRequest::new(self, method, uri.into())
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::Client;
+
+    fn assert_sync<T: Sync>() {}
+
+    #[test]
+    fn test_local_client_impl_sync() {
+        assert_sync::<Client>();
+    }
+}
diff --git a/core/lib/src/local/request.rs b/core/lib/src/local/request.rs
index 0471755b..e6e3fea8 100644
--- a/core/lib/src/local/request.rs
+++ b/core/lib/src/local/request.rs
@@ -111,7 +111,8 @@ impl<'c> LocalRequest<'c> {
 
         // Set up any cookies we know about.
         if let Some(ref jar) = client.cookies {
-            for cookie in jar.borrow().iter() {
+            let cookies = jar.read().expect("LocalRequest::new() read lock");
+            for cookie in cookies.iter() {
                 request.cookies().add_original(cookie.clone().into_owned());
             }
         }
@@ -408,7 +409,7 @@ impl<'c> LocalRequest<'c> {
         // If the client is tracking cookies, updates the internal cookie jar
         // with the changes reflected by `response`.
         if let Some(ref jar) = client.cookies {
-            let mut jar = jar.borrow_mut();
+            let mut jar = jar.write().expect("LocalRequest::_dispatch() write lock");
             let current_time = ::time::now();
             for cookie in response.cookies() {
                 if let Some(expires) = cookie.expires() {