diff --git a/tools/releasetools/non_ab_ota.py b/tools/releasetools/non_ab_ota.py
index 6cd01e401a..99f1faab38 100644
--- a/tools/releasetools/non_ab_ota.py
+++ b/tools/releasetools/non_ab_ota.py
@@ -214,6 +214,7 @@ else if get_stage("%(bcb_dev)s") == "3/3" then
   # Dump fingerprints
   script.Print("Target: {}".format(target_info.fingerprint))
 
+  script.AppendExtra("ifelse(is_mounted(\"/system\"), unmount(\"/system\"));")
   device_specific.FullOTA_InstallBegin()
 
   CopyInstallTools(output_zip)