diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
index 6e3990a..4b1837d 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
@@ -411,10 +411,10 @@
 				throw(_("Customer {0} does not belong to project {1}").format(self.customer,self.project))
 
 	def validate_pos(self):
-		if flt(self.paid_amount) + flt(self.write_off_amount) \
-				- flt(self.grand_total) > 1/(10**(self.precision("grand_total") + 1)) and self.is_return:
-			frappe.throw(_("""Paid amount + Write Off Amount can not be greater than Grand Total"""))
-
+		if self.is_return:
+			if flt(self.paid_amount) + flt(self.write_off_amount) - flt(self.grand_total) < \
+				1/(10**(self.precision("grand_total") + 1)):
+					frappe.throw(_("Paid amount + Write Off Amount can not be greater than Grand Total"))
 
 	def validate_item_code(self):
 		for d in self.get('items'):
diff --git a/erpnext/patches/v7_2/update_assessment_modules.py b/erpnext/patches/v7_2/update_assessment_modules.py
index 9c00902..ec85770 100644
--- a/erpnext/patches/v7_2/update_assessment_modules.py
+++ b/erpnext/patches/v7_2/update_assessment_modules.py
@@ -7,13 +7,15 @@
 	frappe.rename_doc("DocType", "Grade Interval", "Grading Scale Interval", force=True)
 
 	frappe.reload_doc("schools", "doctype", "grading_scale_interval")
-	rename_field("Grading Scale Interval", "to_score", "threshold")
+	if "to_score" in frappe.db.get_table_columns("Grading Scale Interval"):
+		rename_field("Grading Scale Interval", "to_score", "threshold")
 
 	frappe.rename_doc("DocType", "Assessment", "Assessment Plan", force=True)
 
 	#Rename Assessment Results
 	frappe.reload_doc("schools", "doctype", "assessment_plan")
-	rename_field("Assessment Plan", "grading_structure", "grading_scale")
+	if "grading_structure" in frappe.db.get_table_columns("Assessment Plan"):
+		rename_field("Assessment Plan", "grading_structure", "grading_scale")
 
 	frappe.reload_doc("schools", "doctype", "assessment_result")
 	frappe.reload_doc("schools", "doctype", "assessment_result_detail")