Error: Cursor' object has no attribute '_last_executed

I have this cursor

cursor.execute("SELECT price FROM Items WHERE itemID = ( 
                  SELECT item_id FROM Purchases 
                  WHERE purchaseID = %d AND customer_id = %d)", 
                  [self.purchaseID, self.customer])

I get this error

'Cursor' object has no attribute '_last_executed'

But when I try this:

cursor.execute("SELECT price FROM Items WHERE itemID = ( 
                  SELECT item_id FROM Purchases 
                  WHERE purchaseID = 1 AND customer_id = 1)", 
                  )

there is no error. How do I fix this?