diff --git a/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php b/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php
--- a/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php
+++ b/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php
@@ -1763,6 +1763,16 @@
 
     $viewer = $this->getViewer();
 
+    // If we have an omnipotent viewer and no formal space constraints, don't
+    // emit a clause. This primarily enables older migrations to run cleanly,
+    // without fataling because they try to match a `spacePHID` column which
+    // does not exist yet. See T8743, T8746.
+    if ($viewer->isOmnipotent()) {
+      if ($this->spaceIsArchived === null && $this->spacePHIDs === null) {
+        return null;
+      }
+    }
+
     $space_phids = array();
     $include_null = false;