Arrays and foreign keys

Seems that it's not possible to combine arrays and foreign keys ?

CREATE TABLE table1 (
fld1 integer NOT NULL,
number integer,
level integer,
PRIMARY KEY (fld1)
);

CREATE TABLE table2 (
pkey integer NOT NULL,
arvar integer[],
PRIMARY KEY (pkey),
FOREIGN KEY (arvar) REFERENCES table1(fld1)
);

This works, but the following insert complains that

ERROR: Unable to identify an operator '=' for types 'int4' and '_int4'
You will have to retype this query using an explicit cast

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