diff --git a/upgrade_scripts/pg_sphere--1.3.1--1.3.2.sql.in b/upgrade_scripts/pg_sphere--1.3.1--1.3.2.sql.in
index a38db9e..3a80bc7 100644
--- a/upgrade_scripts/pg_sphere--1.3.1--1.3.2.sql.in
+++ b/upgrade_scripts/pg_sphere--1.3.1--1.3.2.sql.in
@@ -28,7 +28,7 @@ COMMENT ON FUNCTION spoly(float8[]) IS
    'creates spoly from array of numbers in radians';
 
 -- add PARALLEL SAFE to spoly_deg(float8[])
-ALTER FUNCTION spoly_deg(float8[]) PARALLEL SAFE;
+ALTER FUNCTION spoly_deg(float8[]) IMMUTABLE STRICT PARALLEL SAFE;
 
 -- update comment on spoly_deg function
 COMMENT ON FUNCTION spoly_deg(float8[]) IS