diff --git a/patches/may_2013/p01_conversion_factor_and_aii.py b/patches/may_2013/p01_conversion_factor_and_aii.py
index 89d82e010d..2fd0d369a5 100644
--- a/patches/may_2013/p01_conversion_factor_and_aii.py
+++ b/patches/may_2013/p01_conversion_factor_and_aii.py
@@ -14,7 +14,7 @@ def execute():
 	webnotes.conn.sql("""update `tabPurchase Invoice Item` pi_item 
 		set conversion_factor = (select ifnull(if(conversion_factor=0, 1, conversion_factor), 1) 
 			from `tabUOM Conversion Detail` 
-			where parent = pi_item.item_code and uom = pi_item.uom
+			where parent = pi_item.item_code and uom = pi_item.uom limit 1
 		)
 		where ifnull(conversion_factor, 0)=0""")