diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index aca8b0d..e654cb6 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -11,7 +11,7 @@ jobs:
   test:
     strategy:
       matrix:
-        pg: [15, 14, 13, 12, 11, 10]
+        pg: [16, 15, 14, 13, 12, 11, 10]
     name: 🐘 PostgreSQL ${{ matrix.pg }}
     runs-on: ubuntu-latest
     container: pgxn/pgxn-tools
diff --git a/sql/currency--0.0.4.sql b/sql/currency--0.0.4.sql
new file mode 100644
index 0000000..a9d8e3c
--- /dev/null
+++ b/sql/currency--0.0.4.sql
@@ -0,0 +1,203 @@
+
+CREATE TYPE currency;
+
+CREATE FUNCTION supported_currencies()
+    RETURNS SETOF currency
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+CREATE FUNCTION currency_in(cstring)
+    RETURNS currency
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+CREATE FUNCTION currency_out(currency)
+    RETURNS cstring
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+CREATE FUNCTION currency_recv(internal)
+    RETURNS currency
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+CREATE FUNCTION currency_send(currency)
+    RETURNS bytea
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+CREATE TYPE currency (
+    internallength = 1,
+    input = currency_in,
+    output = currency_out,
+    send = currency_send,
+    receive = currency_recv,
+    alignment = char,
+    PASSEDBYVALUE
+);
+
+COMMENT ON TYPE currency
+  IS '1-byte ISO 4217 Currency Code';
+
+CREATE FUNCTION currency_lt(currency, currency)
+    RETURNS BOOL
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+COMMENT ON FUNCTION currency_lt(currency, currency) IS 'implementation of < operator';
+
+CREATE FUNCTION currency_le(currency, currency)
+    RETURNS BOOL
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+COMMENT ON FUNCTION currency_le(currency, currency) IS 'implementation of <= operator';
+
+CREATE FUNCTION currency_eq(currency, currency)
+    RETURNS BOOL
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+COMMENT ON FUNCTION currency_eq(currency, currency) IS 'implementation of = operator';
+
+CREATE FUNCTION currency_neq(currency, currency)
+    RETURNS BOOL
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+COMMENT ON FUNCTION currency_neq(currency, currency) IS 'implementation of <> operator';
+
+CREATE FUNCTION currency_ge(currency, currency)
+    RETURNS BOOL
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+COMMENT ON FUNCTION currency_ge(currency, currency) IS 'implementation of >= operator';
+
+CREATE FUNCTION currency_gt(currency, currency)
+    RETURNS BOOL
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+COMMENT ON FUNCTION currency_gt(currency, currency) IS 'implementation of > operator';
+
+CREATE FUNCTION hash_currency(currency)
+    RETURNS integer
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+COMMENT ON FUNCTION hash_currency(currency) IS 'hash';
+
+CREATE OPERATOR < (
+    leftarg = currency,
+    rightarg = currency,
+    procedure = currency_lt,
+    commutator = >,
+    negator   = >=,
+    restrict = scalarltsel,
+    join = scalarltjoinsel
+);
+
+COMMENT ON OPERATOR <(currency, currency) IS 'less than';
+
+CREATE OPERATOR <= (
+    leftarg = currency,
+    rightarg = currency,
+    procedure = currency_le,
+    commutator = >=,
+    negator   = >,
+    restrict = scalarltsel,
+    join = scalarltjoinsel
+);
+
+COMMENT ON OPERATOR <=(currency, currency) IS 'less than or equal';
+
+CREATE OPERATOR = (
+    leftarg = currency,
+    rightarg = currency,
+    procedure = currency_eq,
+    commutator = =,
+    negator   = <>,
+    restrict = eqsel,
+    join = eqjoinsel,
+    HASHES, MERGES
+);
+
+COMMENT ON OPERATOR =(currency, currency) IS 'equal';
+
+CREATE OPERATOR >= (
+    leftarg = currency,
+    rightarg = currency,
+    procedure = currency_ge,
+    commutator = <=,
+    negator   = <,
+    restrict = scalargtsel,
+    join = scalargtjoinsel
+);
+
+COMMENT ON OPERATOR >=(currency, currency) IS 'greater than or equal';
+
+CREATE OPERATOR > (
+    leftarg = currency,
+    rightarg = currency,
+    procedure = currency_gt,
+    commutator = <,
+    negator   = <=,
+    restrict = scalargtsel,
+    join = scalargtjoinsel
+);
+
+COMMENT ON OPERATOR >(currency, currency) IS 'greater than';
+
+CREATE OPERATOR <> (
+    leftarg = currency,
+    rightarg = currency,
+    procedure = currency_neq,
+    commutator = <>,
+    negator = =,
+    restrict = neqsel,
+    join = neqjoinsel
+);
+
+COMMENT ON OPERATOR <>(currency, currency) IS 'not equal';
+
+CREATE FUNCTION currency_cmp(currency, currency)
+    RETURNS int4
+    AS '$libdir/currency.so'
+    LANGUAGE C IMMUTABLE STRICT;
+
+CREATE OPERATOR CLASS currency_ops
+    DEFAULT FOR TYPE currency USING btree AS
+        OPERATOR        1       < ,
+        OPERATOR        2       <= ,
+        OPERATOR        3       = ,
+        OPERATOR        4       >= ,
+        OPERATOR        5       > ,
+        FUNCTION        1       currency_cmp(currency, currency);
+
+CREATE OPERATOR CLASS currency_ops
+    DEFAULT FOR TYPE currency USING hash AS
+        OPERATOR        1       = ,
+        FUNCTION        1       hash_currency(currency);
+
+DO $$
+DECLARE version_num integer;
+BEGIN
+  SELECT current_setting('server_version_num') INTO STRICT version_num;
+  IF version_num > 90600 THEN
+	EXECUTE $E$ ALTER FUNCTION currency_in(cstring) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION currency_out(currency) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION currency_recv(internal) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION currency_send(currency) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION currency_eq(currency, currency) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION currency_neq(currency, currency) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION currency_lt(currency, currency) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION currency_le(currency, currency) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION currency_gt(currency, currency) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION currency_ge(currency, currency) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION currency_cmp(currency, currency) PARALLEL SAFE $E$;
+	EXECUTE $E$ ALTER FUNCTION hash_currency(currency) PARALLEL SAFE $E$;
+  END IF;
+END;
+$$;
+
diff --git a/src/currency.h b/src/currency.h
index 3d3d8c1..100743f 100644
--- a/src/currency.h
+++ b/src/currency.h
@@ -6,6 +6,9 @@
 #include "access/hash.h"
 #include "libpq/pqformat.h"
 #include "funcapi.h"
+#if PG_VERSION_NUM >= 160000
+#include "varatt.h"
+#endif
 
 typedef unsigned char currency;
 
diff --git a/test/expected/parallel_test.out b/test/expected/parallel_test.out
index 20ce82c..859952f 100644
--- a/test/expected/parallel_test.out
+++ b/test/expected/parallel_test.out
@@ -1,6 +1,13 @@
 BEGIN;
 SET max_parallel_workers_per_gather=4;
-SET force_parallel_mode=on;
+DO $$
+BEGIN
+    IF current_setting('server_version_num')::int >= 160000 THEN
+        EXECUTE 'SET debug_parallel_query = on';
+    ELSE
+        EXECUTE 'SET force_parallel_mode = on';
+    END IF;
+END $$;
 CREATE TABLE parallel_test(i int, c currency) WITH (parallel_workers = 4);
 INSERT INTO parallel_test (i, c)
 SELECT i, c.country
diff --git a/test/expected/parallel_test_1.out b/test/expected/parallel_test_1.out
index 4aef4fe..90f9a01 100644
--- a/test/expected/parallel_test_1.out
+++ b/test/expected/parallel_test_1.out
@@ -1,6 +1,13 @@
 BEGIN;
 SET max_parallel_workers_per_gather=4;
-SET force_parallel_mode=on;
+DO $$
+BEGIN
+    IF current_setting('server_version_num')::int >= 160000 THEN
+        EXECUTE 'SET debug_parallel_query = on';
+    ELSE
+        EXECUTE 'SET force_parallel_mode = on';
+    END IF;
+END $$;
 CREATE TABLE parallel_test(i int, c currency) WITH (parallel_workers = 4);
 INSERT INTO parallel_test (i, c)
 SELECT i, c.country
diff --git a/test/sql/parallel_test.sql b/test/sql/parallel_test.sql
index d3aa498..c62ce3d 100644
--- a/test/sql/parallel_test.sql
+++ b/test/sql/parallel_test.sql
@@ -1,6 +1,13 @@
 BEGIN;
 SET max_parallel_workers_per_gather=4;
-SET force_parallel_mode=on;
+DO $$
+BEGIN
+    IF current_setting('server_version_num')::int >= 160000 THEN
+        EXECUTE 'SET debug_parallel_query = on';
+    ELSE
+        EXECUTE 'SET force_parallel_mode = on';
+    END IF;
+END $$;
 
 CREATE TABLE parallel_test(i int, c currency) WITH (parallel_workers = 4);
 INSERT INTO parallel_test (i, c)