diff --git a/src/backend/catalog/system_functions.sql b/src/backend/catalog/system_functions.sql
index 566f308e443..29696b84b35 100644
--- a/src/backend/catalog/system_functions.sql
+++ b/src/backend/catalog/system_functions.sql
@@ -611,14 +611,14 @@ CREATE OR REPLACE FUNCTION
   jsonb_strip_nulls(target jsonb, strip_in_arrays boolean DEFAULT false)
 RETURNS jsonb
 LANGUAGE INTERNAL
-STRICT STABLE PARALLEL SAFE
+STRICT IMMUTABLE PARALLEL SAFE
 AS 'jsonb_strip_nulls';
 
 CREATE OR REPLACE FUNCTION
   json_strip_nulls(target json, strip_in_arrays boolean DEFAULT false)
 RETURNS json
 LANGUAGE INTERNAL
-STRICT STABLE PARALLEL SAFE
+STRICT IMMUTABLE PARALLEL SAFE
 AS 'json_strip_nulls';
 
 -- default normalization form is NFC, per SQL standard