diff --git a/src/applications/diffusion/engine/DiffusionCommitHookEngine.php b/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
--- a/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
+++ b/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
@@ -1133,7 +1133,7 @@
       ->setHookWait(phutil_microseconds_since($hook_start));
 
     $identifier = $this->getRequestIdentifier();
-    if (strlen($identifier)) {
+    if ($identifier !== null && strlen($identifier)) {
       $event->setRequestIdentifier($identifier);
     }