diff --git a/src/applications/config/controller/PhabricatorConfigEditController.php b/src/applications/config/controller/PhabricatorConfigEditController.php
index 5a6f737ea5..c0753e25f1 100644
--- a/src/applications/config/controller/PhabricatorConfigEditController.php
+++ b/src/applications/config/controller/PhabricatorConfigEditController.php
@@ -59,7 +59,7 @@ final class PhabricatorConfigEditController
 
     $e_value = null;
     $errors = array();
-    if ($request->isFormPost()) {
+    if ($request->isFormPost() && !$option->getLocked()) {
 
       $result = $this->readRequest(
         $option,
@@ -100,6 +100,15 @@ final class PhabricatorConfigEditController
       $error_view = id(new AphrontErrorView())
         ->setTitle(pht('You broke everything!'))
         ->setErrors($errors);
+    } else if ($option->getLocked()) {
+      $msg = pht(
+        "This configuration is locked and can not be edited from the web ".
+        "interface.");
+
+      $error_view = id(new AphrontErrorView())
+        ->setTitle(pht('Configuration Locked'))
+        ->setSeverity(AphrontErrorView::SEVERITY_NOTICE)
+        ->appendChild('<p>'.phutil_escape_html($msg).'</p>');
     }
 
     $control = $this->renderControl(
@@ -124,11 +133,15 @@ final class PhabricatorConfigEditController
         id(new AphrontFormMarkupControl())
           ->setLabel(pht('Description'))
           ->setValue($description))
-      ->appendChild($control)
-      ->appendChild(
-        id(new AphrontFormSubmitControl())
-          ->addCancelButton($done_uri)
-          ->setValue(pht('Save Config Entry')));
+      ->appendChild($control);
+
+    if (!$option->getLocked()) {
+      $form
+        ->appendChild(
+          id(new AphrontFormSubmitControl())
+            ->addCancelButton($done_uri)
+            ->setValue(pht('Save Config Entry')));
+    }
 
     $examples = $this->renderExamples($option);
     if ($examples) {
@@ -329,6 +342,10 @@ final class PhabricatorConfigEditController
       ->setValue($display_value)
       ->setName('value');
 
+    if ($option->getLocked()) {
+      $control->setDisabled(true);
+    }
+
     return $control;
   }
 
diff --git a/src/applications/config/controller/PhabricatorConfigGroupController.php b/src/applications/config/controller/PhabricatorConfigGroupController.php
index 0239457729..def0510ca4 100644
--- a/src/applications/config/controller/PhabricatorConfigGroupController.php
+++ b/src/applications/config/controller/PhabricatorConfigGroupController.php
@@ -91,6 +91,10 @@ final class PhabricatorConfigGroupController
         $item->addIcon('edit-grey', pht('Default'));
       }
 
+      if ($option->getLocked()) {
+        $item->addIcon('lock', pht('Locked'));
+      }
+
       $list->addItem($item);
     }
 
diff --git a/src/applications/config/option/PhabricatorConfigOption.php b/src/applications/config/option/PhabricatorConfigOption.php
index c7673001bf..7827626e36 100644
--- a/src/applications/config/option/PhabricatorConfigOption.php
+++ b/src/applications/config/option/PhabricatorConfigOption.php
@@ -12,6 +12,16 @@ final class PhabricatorConfigOption
   private $options;
   private $group;
   private $examples;
+  private $locked;
+
+  public function setLocked($locked) {
+    $this->locked = $locked;
+    return $this;
+  }
+
+  public function getLocked() {
+    return $this->locked;
+  }
 
   public function addExample($value, $description) {
     $this->examples[] = array($value, $description);
diff --git a/src/applications/config/option/PhabricatorCoreConfigOptions.php b/src/applications/config/option/PhabricatorCoreConfigOptions.php
index 301c8b50e6..068dcdbb14 100644
--- a/src/applications/config/option/PhabricatorCoreConfigOptions.php
+++ b/src/applications/config/option/PhabricatorCoreConfigOptions.php
@@ -66,6 +66,8 @@ final class PhabricatorCoreConfigOptions
             "traditional UI strings like 'Submit', you can set this flag to ".
             "disable most of the jokes and easter eggs.")),
        $this->newOption('storage.default-namespace', 'string', 'phabricator')
+        // NOTE: Lock this, since editing it from the web torpedoes an install.
+        ->setLocked(true)
         ->setSummary(
           pht("The namespace that Phabricator databases should use."))
         ->setDescription(
@@ -75,8 +77,7 @@ final class PhabricatorCoreConfigOptions
             "named 'phabricator_differential' by default. You can change ".
             "this namespace if you want. Normally, you should not do this ".
             "unless you are developing Phabricator and using namespaces to ".
-            "separate multiple sandbox datasets."))
-        ->addExample('phabricator', 'Valid Setting'),
+            "separate multiple sandbox datasets.")),
        $this->newOption('environment.append-paths', 'list<string>', null)
         ->setSummary(
           pht("These paths get appended to your \$PATH envrionment variable."))