diff --git a/tools/dtoc/fdt_normal.py b/tools/dtoc/fdt_normal.py
index 4a667a1..eb45742 100644
--- a/tools/dtoc/fdt_normal.py
+++ b/tools/dtoc/fdt_normal.py
@@ -110,7 +110,7 @@
             self._fname = fdt_util.EnsureCompiled(self._fname)
 
             with open(self._fname) as fd:
-                self._fdt = fd.read()
+                self._fdt = bytearray(fd.read())
 
     def GetFdt(self):
         """Get the contents of the FDT