diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8956faa..cd83273 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## 0.1.1 (unreleased)
 
 - Added external binary representation for `vector` type
+- Marked functions as `PARALLEL SAFE`
 
 ## 0.1.0 (2021-04-20)
 
diff --git a/vector--0.1.0--0.1.1.sql b/vector--0.1.0--0.1.1.sql
index 79e0074..959a0d7 100644
--- a/vector--0.1.0--0.1.1.sql
+++ b/vector--0.1.0--0.1.1.sql
@@ -8,3 +8,32 @@ CREATE FUNCTION vector_send(vector) RETURNS bytea
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
 
 ALTER TYPE vector SET ( RECEIVE = vector_recv, SEND = vector_send );
+
+-- functions
+
+ALTER FUNCTION vector_in(cstring, oid, integer) PARALLEL SAFE;
+ALTER FUNCTION vector_out(vector) PARALLEL SAFE;
+ALTER FUNCTION vector_typmod_in(cstring[]) PARALLEL SAFE;
+ALTER FUNCTION vector_recv(internal, oid, integer) PARALLEL SAFE;
+ALTER FUNCTION vector_send(vector) PARALLEL SAFE;
+ALTER FUNCTION l2_distance(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION inner_product(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION cosine_distance(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_dims(vector) PARALLEL SAFE;
+ALTER FUNCTION vector_norm(vector) PARALLEL SAFE;
+ALTER FUNCTION vector_add(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_sub(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_lt(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_le(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_eq(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_ne(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_ge(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_gt(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_cmp(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_l2_squared_distance(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_negative_inner_product(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector_spherical_distance(vector, vector) PARALLEL SAFE;
+ALTER FUNCTION vector(vector, integer, boolean) PARALLEL SAFE;
+ALTER FUNCTION array_to_vector(integer[], integer, boolean) PARALLEL SAFE;
+ALTER FUNCTION array_to_vector(real[], integer, boolean) PARALLEL SAFE;
+ALTER FUNCTION array_to_vector(double precision[], integer, boolean) PARALLEL SAFE;
diff --git a/vector--0.1.1.sql b/vector--0.1.1.sql
index 9ae9887..73892c0 100644
--- a/vector--0.1.1.sql
+++ b/vector--0.1.1.sql
@@ -6,19 +6,19 @@
 CREATE TYPE vector;
 
 CREATE FUNCTION vector_in(cstring, oid, integer) RETURNS vector
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_out(vector) RETURNS cstring
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_typmod_in(cstring[]) RETURNS integer
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_recv(internal, oid, integer) RETURNS vector
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_send(vector) RETURNS bytea
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE TYPE vector (
 	INPUT     = vector_in,
@@ -31,71 +31,71 @@ CREATE TYPE vector (
 -- functions
 
 CREATE FUNCTION l2_distance(vector, vector) RETURNS float8
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION inner_product(vector, vector) RETURNS float8
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION cosine_distance(vector, vector) RETURNS float8
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_dims(vector) RETURNS integer
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_norm(vector) RETURNS float8
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_add(vector, vector) RETURNS vector
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_sub(vector, vector) RETURNS vector
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 -- private functions
 
 CREATE FUNCTION vector_lt(vector, vector) RETURNS bool
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_le(vector, vector) RETURNS bool
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_eq(vector, vector) RETURNS bool
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_ne(vector, vector) RETURNS bool
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_ge(vector, vector) RETURNS bool
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_gt(vector, vector) RETURNS bool
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_cmp(vector, vector) RETURNS int4
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_l2_squared_distance(vector, vector) RETURNS float8
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_negative_inner_product(vector, vector) RETURNS float8
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION vector_spherical_distance(vector, vector) RETURNS float8
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 -- cast functions
 
 CREATE FUNCTION vector(vector, integer, boolean) RETURNS vector
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION array_to_vector(integer[], integer, boolean) RETURNS vector
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION array_to_vector(real[], integer, boolean) RETURNS vector
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION array_to_vector(double precision[], integer, boolean) RETURNS vector
-	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT;
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 -- casts