diff --git a/rct229/rulesets/ashrae9012019/section5/section5rule28.py b/rct229/rulesets/ashrae9012019/section5/section5rule28.py
index 882866e3b..f6c91a2ec 100644
--- a/rct229/rulesets/ashrae9012019/section5/section5rule28.py
+++ b/rct229/rulesets/ashrae9012019/section5/section5rule28.py
@@ -210,7 +210,7 @@ def manual_check_required(self, context, calc_vals=None, data=None):
                     manual_check_required_flag = data["manual_check_required_flag"]
                     # if exterior mixed and required manual check
                     return (
-                        data["surface_id_b"] == SCC.EXTERIOR_MIXED
+                        data["scc_dict_b"][data["surface_id_b"]] == SCC.EXTERIOR_MIXED
                         and manual_check_required_flag
                     )