diff --git a/releasetools/galaxys2_ota_from_target_files b/releasetools/galaxys2_ota_from_target_files
index 7a41ec6..61cb7cc 100755
--- a/releasetools/galaxys2_ota_from_target_files
+++ b/releasetools/galaxys2_ota_from_target_files
@@ -61,7 +61,9 @@ def WriteFullOTAPackage(input_zip, output_zip):
   AppendAssertions(script, input_zip)
   device_specific.FullOTA_Assertions()
   if OPTIONS.backuptool:
+    script.Mount("/system")
     script.RunBackup("backup")
+    script.Unmount("/system")
 
   script.ShowProgress(0.5, 0)