diff --git a/src/main/scala/app/SettingsController.scala b/src/main/scala/app/SettingsController.scala
index aea36c1..9fcbdd5 100644
--- a/src/main/scala/app/SettingsController.scala
+++ b/src/main/scala/app/SettingsController.scala
@@ -2,15 +2,15 @@
 
 import service._
 import util.Directory._
-import util.OwnerOnlyAuthenticator
+import util.{UsersOnlyAuthenticator, OwnerOnlyAuthenticator}
 import jp.sf.amateras.scalatra.forms._
 import org.apache.commons.io.FileUtils
 
 class SettingsController extends SettingsControllerBase
-  with RepositoryService with AccountService with OwnerOnlyAuthenticator
+  with RepositoryService with AccountService with OwnerOnlyAuthenticator with UsersOnlyAuthenticator
 
 trait SettingsControllerBase extends ControllerBase {
-  self: RepositoryService with AccountService with OwnerOnlyAuthenticator =>
+  self: RepositoryService with AccountService with OwnerOnlyAuthenticator with UsersOnlyAuthenticator =>
 
   case class OptionsForm(description: Option[String], defaultBranch: String, isPrivate: Boolean)
   
@@ -71,6 +71,14 @@
   })
 
   /**
+   * JSON API for collaborator completion.
+   */
+  get("/:owner/:repository/settings/collaborators/proposals")(usersOnly {
+    contentType = formats("json")
+    org.json4s.jackson.Serialization.write(Map("options" -> getAllUsers.map(_.userName).toArray))
+  })
+
+  /**
    * Add the collaborator.
    */
   post("/:owner/:repository/settings/collaborators/add", collaboratorForm)(ownerOnly { form =>
diff --git a/src/main/twirl/settings/collaborators.scala.html b/src/main/twirl/settings/collaborators.scala.html
index a174d21..c7aef83 100644
--- a/src/main/twirl/settings/collaborators.scala.html
+++ b/src/main/twirl/settings/collaborators.scala.html
@@ -21,3 +21,13 @@
     </form>
   }
 }
+<script>
+$('#userName').typeahead({
+  source: function (query, process) {
+    return $.get('@path/@repository.owner/@repository.name/settings/collaborators/proposals', { query: query },
+      function (data) {
+        return process(data.options);
+      });
+  }
+});
+</script>
\ No newline at end of file