diff --git a/modules/kvformat/filterx-func-parse-kv.c b/modules/kvformat/filterx-func-parse-kv.c
index 5e8887408..7ad457622 100644
--- a/modules/kvformat/filterx-func-parse-kv.c
+++ b/modules/kvformat/filterx-func-parse-kv.c
@@ -145,6 +145,15 @@ _generate(FilterXExprGenerator *s, FilterXObject *fillable)
   return result;
 }
 
+static FilterXExpr *
+_optimize(FilterXExpr *s)
+{
+  FilterXFunctionParseKV *self = (FilterXFunctionParseKV *) s;
+
+  self->msg = filterx_expr_optimize(self->msg);
+  return filterx_generator_function_optimize_method(&self->super);
+}
+
 static gboolean
 _init(FilterXExpr *s, GlobalConfig *cfg)
 {
@@ -274,6 +283,7 @@ filterx_function_parse_kv_new(FilterXFunctionArgs *args, GError **error)
   filterx_generator_function_init_instance(&self->super, "parse_kv");
   self->super.super.generate = _generate;
   self->super.super.create_container = filterx_generator_create_dict_container;
+  self->super.super.super.optimize = _optimize;
   self->super.super.super.init = _init;
   self->super.super.super.deinit = _deinit;
   self->super.super.super.free_fn = _free;