diff --git a/static/directives/config/config-setup-tool.html b/static/directives/config/config-setup-tool.html
index 09368ba1f..d8fc2b800 100644
--- a/static/directives/config/config-setup-tool.html
+++ b/static/directives/config/config-setup-tool.html
@@ -1239,6 +1239,17 @@
               </div>
             </td>
           </tr>
+          <tr>
+            <td class="non-input">Prefix username autocompletion:</td>
+            <td colspan="2">
+              <div class="config-bool-field" binding="config.FEATURE_PARTIAL_USER_AUTOCOMPLETE">
+                Allow prefix username autocompletion
+              </div>
+              <div class="help-text">
+                 If disabled, autocompletion for users will only match on exact usernames.
+              </div>
+            </td>
+          </tr>
           <tr ng-show="config.FEATURE_MAILING">
             <td class="non-input">Team Invitations:</td>
             <td colspan="2">
diff --git a/util/config/configutil.py b/util/config/configutil.py
index 7db5d4578..ace6e02a5 100644
--- a/util/config/configutil.py
+++ b/util/config/configutil.py
@@ -20,6 +20,7 @@ def add_enterprise_config_defaults(config_obj, current_secret_key, hostname):
   config_obj['FEATURE_CHANGE_TAG_EXPIRATION'] = config_obj.get('FEATURE_CHANGE_TAG_EXPIRATION',
                                                                True)
   config_obj['FEATURE_DIRECT_LOGIN'] = config_obj.get('FEATURE_DIRECT_LOGIN', True)
+  config_obj['FEATURE_PARTIAL_USER_AUTOCOMPLETE'] = config_obj.get('FEATURE_PARTIAL_USER_AUTOCOMPLETE', True)
 
   # Default features that are off.
   config_obj['FEATURE_MAILING'] = config_obj.get('FEATURE_MAILING', False)