diff --git a/src/daemon/PhutilDaemonOverseer.php b/src/daemon/PhutilDaemonOverseer.php
--- a/src/daemon/PhutilDaemonOverseer.php
+++ b/src/daemon/PhutilDaemonOverseer.php
@@ -144,6 +144,13 @@
       } else if ($pid) {
         exit(0);
       }
+
+      if (function_exists('posix_setsid')) {
+        $sid = posix_setsid();
+        if ($sid === -1) {
+          throw new Exception(pht('Unable to setsid!'));
+        }
+      }
     }
 
     $this->modules = PhutilDaemonOverseerModule::getAllModules();