diff --git a/src/applications/harbormaster/step/HarbormasterWaitForPreviousBuildStepImplementation.php b/src/applications/harbormaster/step/HarbormasterWaitForPreviousBuildStepImplementation.php
--- a/src/applications/harbormaster/step/HarbormasterWaitForPreviousBuildStepImplementation.php
+++ b/src/applications/harbormaster/step/HarbormasterWaitForPreviousBuildStepImplementation.php
@@ -73,26 +73,26 @@
       }
     }
 
-    $buildables = id(new HarbormasterBuildableQuery())
-      ->setViewer(PhabricatorUser::getOmnipotentUser())
-      ->withBuildablePHIDs($build_objects)
-      ->withManualBuildables(false)
-      ->execute();
-    $buildable_phids = mpull($buildables, 'getPHID');
-
-    if (!$buildable_phids) {
-      return array();
-    }
-
-    $builds = id(new HarbormasterBuildQuery())
-      ->setViewer(PhabricatorUser::getOmnipotentUser())
-      ->withBuildablePHIDs($buildable_phids)
-      ->withBuildPlanPHIDs(array($plan->getPHID()))
-      ->execute();
-
-    foreach ($builds as $build) {
-      if (!$build->isComplete()) {
-        $blockers[] = pht('Build %d', $build->getID());
+    if ($build_objects) {
+      $buildables = id(new HarbormasterBuildableQuery())
+        ->setViewer(PhabricatorUser::getOmnipotentUser())
+        ->withBuildablePHIDs($build_objects)
+        ->withManualBuildables(false)
+        ->execute();
+      $buildable_phids = mpull($buildables, 'getPHID');
+
+      if ($buildable_phids) {
+        $builds = id(new HarbormasterBuildQuery())
+          ->setViewer(PhabricatorUser::getOmnipotentUser())
+          ->withBuildablePHIDs($buildable_phids)
+          ->withBuildPlanPHIDs(array($plan->getPHID()))
+          ->execute();
+
+        foreach ($builds as $build) {
+          if (!$build->isComplete()) {
+            $blockers[] = pht('Build %d', $build->getID());
+          }
+        }
       }
     }