diff --git a/src/applications/differential/controller/DifferentialInlineCommentEditController.php b/src/applications/differential/controller/DifferentialInlineCommentEditController.php
--- a/src/applications/differential/controller/DifferentialInlineCommentEditController.php
+++ b/src/applications/differential/controller/DifferentialInlineCommentEditController.php
@@ -120,7 +120,9 @@
 
   protected function canEditInlineComment(
     PhabricatorUser $viewer,
-    DifferentialInlineComment $inline) {
+    PhabricatorInlineComment $inline) {
+
+    assert($inline instanceof DifferentialInlineComment);
 
     // Only the author may edit a comment.
     if ($inline->getAuthorPHID() != $viewer->getPHID()) {
diff --git a/src/applications/diffusion/controller/DiffusionInlineCommentController.php b/src/applications/diffusion/controller/DiffusionInlineCommentController.php
--- a/src/applications/diffusion/controller/DiffusionInlineCommentController.php
+++ b/src/applications/diffusion/controller/DiffusionInlineCommentController.php
@@ -87,7 +87,9 @@
 
   protected function canEditInlineComment(
     PhabricatorUser $viewer,
-    PhabricatorAuditInlineComment $inline) {
+    PhabricatorInlineComment $inline) {
+
+    assert($inline instanceof PhabricatorAuditInlineComment);
 
     // Only the author may edit a comment.
     if ($inline->getAuthorPHID() != $viewer->getPHID()) {
diff --git a/src/infrastructure/diff/PhabricatorInlineCommentController.php b/src/infrastructure/diff/PhabricatorInlineCommentController.php
--- a/src/infrastructure/diff/PhabricatorInlineCommentController.php
+++ b/src/infrastructure/diff/PhabricatorInlineCommentController.php
@@ -11,6 +11,8 @@
   abstract protected function loadObjectOwnerPHID(
     PhabricatorInlineComment $inline);
   abstract protected function newContainerObject();
+  abstract protected function canEditInlineComment(
+    PhabricatorUser $viewer, PhabricatorInlineComment $inline);
 
   final protected function getContainerObject() {
     if ($this->containerObject === null) {