diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index 080ba7456f..fd8be406e7 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -530,6 +530,7 @@ phutil_register_library_map(array(
     'DiffusionPushLogListController' => 'applications/diffusion/controller/DiffusionPushLogListController.php',
     'DiffusionQuery' => 'applications/diffusion/query/DiffusionQuery.php',
     'DiffusionRawDiffQuery' => 'applications/diffusion/query/rawdiff/DiffusionRawDiffQuery.php',
+    'DiffusionRefNotFoundException' => 'applications/diffusion/exception/DiffusionRefNotFoundException.php',
     'DiffusionRenameHistoryQuery' => 'applications/diffusion/query/DiffusionRenameHistoryQuery.php',
     'DiffusionRepositoryController' => 'applications/diffusion/controller/DiffusionRepositoryController.php',
     'DiffusionRepositoryCreateController' => 'applications/diffusion/controller/DiffusionRepositoryCreateController.php',
@@ -3172,6 +3173,7 @@ phutil_register_library_map(array(
     ),
     'DiffusionQuery' => 'PhabricatorQuery',
     'DiffusionRawDiffQuery' => 'DiffusionQuery',
+    'DiffusionRefNotFoundException' => 'Exception',
     'DiffusionRepositoryController' => 'DiffusionController',
     'DiffusionRepositoryCreateController' => 'DiffusionRepositoryEditController',
     'DiffusionRepositoryDefaultController' => 'DiffusionController',
diff --git a/src/applications/diffusion/exception/DiffusionRefNotFoundException.php b/src/applications/diffusion/exception/DiffusionRefNotFoundException.php
new file mode 100644
index 0000000000..8dda27d072
--- /dev/null
+++ b/src/applications/diffusion/exception/DiffusionRefNotFoundException.php
@@ -0,0 +1,16 @@
+<?php
+
+final class DiffusionRefNotFoundException extends Exception {
+
+  private $ref;
+
+  public function setRef($ref) {
+    $this->ref = $ref;
+    return $this;
+  }
+
+  public function getRef() {
+    return $this->ref;
+  }
+
+}
diff --git a/src/applications/diffusion/request/DiffusionRequest.php b/src/applications/diffusion/request/DiffusionRequest.php
index db64e1841c..dd20d7380e 100644
--- a/src/applications/diffusion/request/DiffusionRequest.php
+++ b/src/applications/diffusion/request/DiffusionRequest.php
@@ -4,11 +4,8 @@
  * Contains logic to parse Diffusion requests, which have a complicated URI
  * structure.
  *
- *
  * @task new Creating Requests
  * @task uri Managing Diffusion URIs
- *
- * @group diffusion
  */
 abstract class DiffusionRequest {
 
@@ -644,17 +641,18 @@ abstract class DiffusionRequest {
     }
 
     if ($this->getSupportsBranches()) {
-      $branch = $this->getResolvableBranchName($this->getBranch());
+      $ref = $this->getResolvableBranchName($this->getBranch());
     } else {
-      $branch = 'HEAD';
+      $ref = 'HEAD';
     }
 
-    $results = $this->resolveRefs(array($branch));
+    $results = $this->resolveRefs(array($ref));
 
-    $matches = idx($results, $branch, array());
+    $matches = idx($results, $ref, array());
     if (count($matches) !== 1) {
-      throw new Exception(
-        pht('Ref "%s" is ambiguous or does not exist.', $branch));
+      $message = pht('Ref "%s" is ambiguous or does not exist.', $ref);
+      throw id(new DiffusionRefNotFoundException($message))
+        ->setRef($ref);
     }
 
     $this->stableCommit = idx(head($matches), 'identifier');