diff --git a/src/applications/diffusion/protocol/DiffusionCommandEngine.php b/src/applications/diffusion/protocol/DiffusionCommandEngine.php
index 53a086db33..d7da62b11d 100644
--- a/src/applications/diffusion/protocol/DiffusionCommandEngine.php
+++ b/src/applications/diffusion/protocol/DiffusionCommandEngine.php
@@ -135,6 +135,11 @@ abstract class DiffusionCommandEngine extends Phobject {
 
     $future->setEnv($env);
 
+    // See T13108. By default, don't let any cluster command run indefinitely
+    // to try to avoid cases where `git fetch` hangs for some reason and we're
+    // left sitting with a held lock forever.
+    $future->setTimeout(phutil_units('15 minutes in seconds'));
+
     return $future;
   }