Detecting Of Record Does Not Work In If Query

Edit: Newer mind. I tested this query more after writing this, and now it seems to work!
I hope it continues to work. 
In following query, else is never executed.


CREATE PROCEDURE Put_into_basket
(    @Product_code varchar(20))
AS
BEGIN
    SET NOCOUNT ON;
IF NOT EXISTS(SELECT * FROM dbo.t_shopping_basket WHERE Product_code=@Product_code)
    BEGIN
        INSERT dbo.t_shopping_basket (Product_code, Name,Price)
        SELECT Product_code, Name,Price
        FROM dbo.t_product
        WHERE Product_code= @Product_code
    END
ELSE    --this part is never executed
    BEGIN   
        UPDATE dbo.t_shopping_basket
        SET Quantity=Quantity+1
        WHERE Product_code=@Product_code
    END
END
GO

 The query should test if there is a record or row with Product_code=@Product_code.

If there is not, that is the first part, one such row is inserted. Quantity has a default value of 1. Insertion works, one row is inserted. At least sort of.

If there is already record, That's later part, Quantity is increased by 1. That too works, if ran separately.
But when I test query, it never runs the quantity+1 part.