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
@@ -1282,7 +1282,7 @@
   }
 
   private function buildUnitMessagesView(
-    $diff,
+    DifferentialDiff $diff,
     DifferentialRevision $revision) {
     $viewer = $this->getViewer();
 
@@ -1310,14 +1310,8 @@
       return null;
     }
 
-    $excuse = null;
-    if ($diff->hasDiffProperty('arc:unit-excuse')) {
-      $excuse = $diff->getProperty('arc:unit-excuse');
-    }
-
     return id(new HarbormasterUnitSummaryView())
       ->setViewer($viewer)
-      ->setExcuse($excuse)
       ->setBuildable($diff->getBuildable())
       ->setUnitMessages($diff->getUnitMessages())
       ->setLimit(5)
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
@@ -42,7 +42,7 @@
   private $unsavedChangesets = array();
   private $changesets = self::ATTACHABLE;
   private $revision = self::ATTACHABLE;
-  private $properties = array();
+  private $properties = self::ATTACHABLE;
   private $buildable = self::ATTACHABLE;
 
   private $unitMessages = self::ATTACHABLE;
@@ -338,6 +338,9 @@
   }
 
   public function attachProperty($key, $value) {
+    if (!is_array($this->properties)) {
+      $this->properties = array();
+    }
     $this->properties[$key] = $value;
     return $this;
   }
diff --git a/src/applications/harbormaster/view/HarbormasterUnitSummaryView.php b/src/applications/harbormaster/view/HarbormasterUnitSummaryView.php
--- a/src/applications/harbormaster/view/HarbormasterUnitSummaryView.php
+++ b/src/applications/harbormaster/view/HarbormasterUnitSummaryView.php
@@ -5,7 +5,6 @@
   private $buildable;
   private $messages;
   private $limit;
-  private $excuse;
   private $showViewAll;
 
   public function setBuildable(HarbormasterBuildable $buildable) {
@@ -23,11 +22,6 @@
     return $this;
   }
 
-  public function setExcuse($excuse) {
-    $this->excuse = $excuse;
-    return $this;
-  }
-
   public function setShowViewAll($show_view_all) {
     $this->showViewAll = $show_view_all;
     return $this;
@@ -88,21 +82,6 @@
       $table->setLimit($this->limit);
     }
 
-    $excuse = $this->excuse;
-    if (strlen($excuse)) {
-      $excuse_icon = id(new PHUIIconView())
-        ->setIcon('fa-commenting-o red');
-
-      $table->setNotice(
-        array(
-          $excuse_icon,
-          ' ',
-          phutil_tag('strong', array(), pht('Excuse:')),
-          ' ',
-          $excuse,
-        ));
-    }
-
     $box->setTable($table);
 
     return $box;