Google Sheets SUMIF with date doesn't sum

I want to sum the amounts column B that have a receipt date in column A in 2018. I tried using this SUMIF formula for that:

=SUMIF(A2:A4,YEAR(2018),B2:B4)

I expected the result to be Fr. 5 but Google Sheet returns 0. What am I doing wrong?

(here's a link to this example table in Google Sheets)

Additional info:

• Column A is formatted as date and column B as currency
• The date format in Switzerland is dd.MM.yyyy
• Google Sheet uses Fr. as a currency symbol for the Swiss Franc, the currency used in Switzerland.