diff --git a/meta/classes/rootfs.bbclass b/meta/classes/rootfs.bbclass
index b3faade..63735d4 100644
--- a/meta/classes/rootfs.bbclass
+++ b/meta/classes/rootfs.bbclass
@@ -198,11 +198,14 @@ python do_rootfs_install() {
         if (d.getVarFlag(cmd, 'isar-apt-lock') or "") == "acquire-before":
             lock = bb.utils.lockfile(d.getVar("REPO_ISAR_DIR") + "/isar.lock",
                                      shared=True)
+        else:
+            lock = ""
 
         bb.build.exec_func(cmd, d)
 
         if (d.getVarFlag(cmd, 'isar-apt-lock') or "") == "release-after":
-            bb.utils.unlockfile(lock)
+            if (lock != ""):
+                bb.utils.unlockfile(lock)
     progress_reporter.finish()
 }
 addtask rootfs_install before do_rootfs_postprocess after do_unpack