diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -5058,6 +5058,7 @@
     'DifferentialDiff' => array(
       'DifferentialDAO',
       'PhabricatorPolicyInterface',
+      'PhabricatorExtendedPolicyInterface',
       'HarbormasterBuildableInterface',
       'HarbormasterCircleCIBuildableInterface',
       'PhabricatorApplicationTransactionInterface',
diff --git a/src/applications/differential/controller/DifferentialRevisionViewController.php b/src/applications/differential/controller/DifferentialRevisionViewController.php
--- a/src/applications/differential/controller/DifferentialRevisionViewController.php
+++ b/src/applications/differential/controller/DifferentialRevisionViewController.php
@@ -16,18 +16,17 @@
 
     $revision = id(new DifferentialRevisionQuery())
       ->withIDs(array($this->revisionID))
-      ->setViewer($request->getUser())
+      ->setViewer($viewer)
       ->needRelationships(true)
       ->needReviewerStatus(true)
       ->needReviewerAuthority(true)
       ->executeOne();
-
     if (!$revision) {
       return new Aphront404Response();
     }
 
     $diffs = id(new DifferentialDiffQuery())
-      ->setViewer($request->getUser())
+      ->setViewer($viewer)
       ->withRevisionIDs(array($this->revisionID))
       ->execute();
     $diffs = array_reverse($diffs, $preserve_keys = true);
diff --git a/src/applications/differential/storage/DifferentialDiff.php b/src/applications/differential/storage/DifferentialDiff.php
--- a/src/applications/differential/storage/DifferentialDiff.php
+++ b/src/applications/differential/storage/DifferentialDiff.php
@@ -4,6 +4,7 @@
   extends DifferentialDAO
   implements
     PhabricatorPolicyInterface,
+    PhabricatorExtendedPolicyInterface,
     HarbormasterBuildableInterface,
     HarbormasterCircleCIBuildableInterface,
     PhabricatorApplicationTransactionInterface,
@@ -429,7 +430,7 @@
 
   public function getPolicy($capability) {
     if ($this->hasRevision()) {
-      return $this->getRevision()->getPolicy($capability);
+      return PhabricatorPolicies::getMostOpenPolicy();
     }
 
     return $this->viewPolicy;
@@ -440,7 +441,7 @@
       return $this->getRevision()->hasAutomaticCapability($capability, $viewer);
     }
 
-    return ($this->getAuthorPHID() == $viewer->getPhid());
+    return ($this->getAuthorPHID() == $viewer->getPHID());
   }
 
   public function describeAutomaticCapability($capability) {
@@ -448,10 +449,31 @@
       return pht(
         'This diff is attached to a revision, and inherits its policies.');
     }
+
     return pht('The author of a diff can see it.');
   }
 
 
+/* -(  PhabricatorExtendedPolicyInterface  )--------------------------------- */
+
+
+  public function getExtendedPolicy($capability, PhabricatorUser $viewer) {
+    $extended = array();
+
+    switch ($capability) {
+      case PhabricatorPolicyCapability::CAN_VIEW:
+        if ($this->hasRevision()) {
+          $extended[] = array(
+            $this->getRevision(),
+            PhabricatorPolicyCapability::CAN_VIEW,
+          );
+        }
+        break;
+    }
+
+    return $extended;
+  }
+
 
 /* -(  HarbormasterBuildableInterface  )------------------------------------- */