diff --git a/tools/dtoc/fdt.py b/tools/dtoc/fdt.py
index fd0f3e9..2589be9 100644
--- a/tools/dtoc/fdt.py
+++ b/tools/dtoc/fdt.py
@@ -272,6 +272,7 @@
         the FDT is synced
         """
         self._offset = None
+        self.dirty = True
 
 class Node:
     """A device tree node