diff --git a/src/applications/diffusion/controller/DiffusionBrowseController.php b/src/applications/diffusion/controller/DiffusionBrowseController.php
--- a/src/applications/diffusion/controller/DiffusionBrowseController.php
+++ b/src/applications/diffusion/controller/DiffusionBrowseController.php
@@ -652,6 +652,15 @@
         $rename_query->setOldCommit($grandparent);
         $rename_query->setViewer($request->getUser());
         $old_filename = $rename_query->loadOldFilename();
+        if (!$old_filename) {
+          $rename_notice = id(new PHUIInfoView())
+          ->setSeverity(PHUIInfoView::SEVERITY_WARNING)
+          ->setTitle(pht('Unable to Continue'))
+          ->appendChild(
+            pht(
+              'Unable to continue tracing the history of this file because '.
+              'this commit was not imported correctly.'));
+        }
         $was_created = $rename_query->getWasCreated();
       }
     }
diff --git a/src/applications/diffusion/query/DiffusionRenameHistoryQuery.php b/src/applications/diffusion/query/DiffusionRenameHistoryQuery.php
--- a/src/applications/diffusion/query/DiffusionRenameHistoryQuery.php
+++ b/src/applications/diffusion/query/DiffusionRenameHistoryQuery.php
@@ -30,15 +30,20 @@
     return $this->oldCommit;
   }
 
+  /**
+   * @return string|null Path to previous filename
+   */
   public function loadOldFilename() {
     $drequest = $this->request;
     $repository_id = $drequest->getRepository()->getID();
     $conn_r = id(new PhabricatorRepository())->establishConnection('r');
 
     $commit_id = $this->loadCommitId($this->oldCommit);
-    $old_commit_sequence = $this->loadCommitSequence($commit_id);
-
     $path = '/'.$drequest->getPath();
+    $old_commit_sequence = $this->loadCommitSequence($commit_id);
+    if ($old_commit_sequence === null) {
+      return null;
+    }
     $commit_id = $this->loadCommitId($drequest->getCommit());
 
     do {
@@ -86,6 +91,9 @@
     return $commit->getID();
   }
 
+  /**
+   * @return string|null commitSequence ID
+   */
   private function loadCommitSequence($commit_id) {
     $conn_r = id(new PhabricatorRepository())->establishConnection('r');
     $path_change = queryfx_one(
@@ -97,6 +105,9 @@
       PhabricatorRepository::TABLE_PATHCHANGE,
       $this->request->getRepository()->getID(),
       $commit_id);
+    if ($path_change === null) {
+      return null;
+    }
     return reset($path_change);
   }