diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 8a8a613..513fce5 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -1313,7 +1313,11 @@
     key = "super_%s_partition_list" % partition_group
     merged_dict[key] = uniq_concat(
         framework_dict.get(key, ""), vendor_dict.get(key, ""))
-
+  # in the case that vendor is on s build, but is taking a v3 -> v3 vabc ota, we want to fallback to v2
+  if "vabc_cow_version" not in vendor_dict or "vabc_cow_version" not in framework_dict:
+    merged_dict["vabc_cow_version"] = '2'
+  else:
+    merged_dict["vabc_cow_version"] = min(vendor_dict["vabc_cow_version"], framework_dict["vabc_cow_version"])
   # Various other flags should be copied from the vendor dict, if defined.
   for key in ("virtual_ab", "virtual_ab_retrofit", "lpmake",
               "super_metadata_device", "super_partition_error_limit",