diff --git a/src/applications/phriction/application/PhabricatorPhrictionApplication.php b/src/applications/phriction/application/PhabricatorPhrictionApplication.php
--- a/src/applications/phriction/application/PhabricatorPhrictionApplication.php
+++ b/src/applications/phriction/application/PhabricatorPhrictionApplication.php
@@ -61,7 +61,7 @@
         'new/'                        => 'PhrictionNewController',
         'move/(?P<id>[1-9]\d*)/' => 'PhrictionMoveController',
 
-        'preview/(?P<slug>.*/)' => 'PhrictionMarkupPreviewController',
+        'preview/' => 'PhrictionMarkupPreviewController',
         'diff/(?P<id>[1-9]\d*)/' => 'PhrictionDiffController',
 
         $this->getEditRoutePattern('document/edit/')
diff --git a/src/applications/phriction/controller/PhrictionEditController.php b/src/applications/phriction/controller/PhrictionEditController.php
--- a/src/applications/phriction/controller/PhrictionEditController.php
+++ b/src/applications/phriction/controller/PhrictionEditController.php
@@ -316,9 +316,17 @@
       ->setBackground(PHUIObjectBoxView::WHITE_CONFIG)
       ->setForm($form);
 
+    $preview_uri = '/phriction/preview/';
+    $preview_uri = new PhutilURI(
+      $preview_uri,
+      array(
+        'slug' => $document->getSlug(),
+      ));
+    $preview_uri = phutil_string_cast($preview_uri);
+
     $preview = id(new PHUIRemarkupPreviewPanel())
       ->setHeader($content->getTitle())
-      ->setPreviewURI('/phriction/preview/'.$document->getSlug())
+      ->setPreviewURI($preview_uri)
       ->setControlID('document-textarea')
       ->setPreviewType(PHUIRemarkupPreviewPanel::DOCUMENT);
 
diff --git a/src/applications/phriction/controller/PhrictionMarkupPreviewController.php b/src/applications/phriction/controller/PhrictionMarkupPreviewController.php
--- a/src/applications/phriction/controller/PhrictionMarkupPreviewController.php
+++ b/src/applications/phriction/controller/PhrictionMarkupPreviewController.php
@@ -8,7 +8,7 @@
     $viewer = $request->getUser();
 
     $text = $request->getStr('text');
-    $slug = $request->getURIData('slug');
+    $slug = $request->getStr('slug');
 
     $output = PhabricatorMarkupEngine::renderOneObject(
       id(new PhabricatorMarkupOneOff())