diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index 54bb857..f30f787 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -57,7 +57,7 @@
   Returns:
     The number of bytes based on a 1K block_size.
   """
-  cmd = ["du", "-k", "-s", path]
+  cmd = ["du", "-b", "-k", "-s", path]
   output = common.RunAndCheckOutput(cmd, verbose=False)
   return int(output.split()[0]) * 1024