GiST index question

I have a table that I have defined as:

CREATE TABLE test (
"id" SERIAL PRIMARY KEY,
"first_path" path NOT NULL,
"second_path" path NOT NULL
);

I am attempting to create a GiST index on the two “path” columns using:

CREATE INDEX  "idx_test_first_path" ON test USING gist(first_path);
CREATE INDEX  "idx_test_second_path" ON test USING gist(second_path);

I am getting this error:

Error : ERROR:  data type path has no default operator class for access method "gist"

Is it that I am not allowed to create an index on the path data type or do I need to enable an extension for this to work? Thanks in advance for your help.
—
Eric Fleming