--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7574,6 +7574,19 @@ StartupXLOG(void)
                    LWLockRelease(XidGenLock);
                }
+               /*
+                * Assign subtransaction xids to the top level xid if the
+                * record has that information. This is required at most
+                * once per subtransactions.
+                */
+               if (TransactionIdIsValid(xlogreader->toplevel_xid) &&
+                   standbyState >= STANDBY_INITIALIZED)
+               {
+                   Assert(XLogStandbyInfoActive());
+                   ProcArrayApplyXidAssignment(xlogreader->toplevel_xid,
+                                               1, &record->xl_xid);
+               }
+
                /*
                 * Before replaying this record, check if this record causes
                 * the current timeline to change. The record is already