diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index 7639ffd..252b1d5 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -410,7 +410,7 @@
       build_command.append("--casefold")
     if (needs_compress or prop_dict.get("f2fs_compress") == "true"):
       build_command.append("--compression")
-    if (prop_dict.get("mount_point") != "data"):
+    if "ro_mount_point" in prop_dict:
       build_command.append("--readonly")
     if (prop_dict.get("f2fs_compress") == "true"):
       build_command.append("--sldc")
@@ -757,6 +757,8 @@
     if not copy_prop(prop, "extfs_rsv_pct"):
       d["extfs_rsv_pct"] = "0"
 
+    d["ro_mount_point"] = "1"
+
   # Copy partition-specific properties.
   d["mount_point"] = mount_point
   if mount_point == "system":