diff --git a/data/json/recipes/armor/arms.json b/data/json/recipes/armor/arms.json
index b34fa5d7ce269..e6ba89be57a25 100644
--- a/data/json/recipes/armor/arms.json
+++ b/data/json/recipes/armor/arms.json
@@ -229,7 +229,7 @@
     "time": "120 m",
     "autolearn": true,
     "components": [ [ [ "sheet_metal", 1 ] ], [ [ "cordage_6_leather", 8 ] ] ],
-    "proficiencies": [ { "proficiency": "prof_metalworking" }, { "proficiency": "prof_case_hardening" } ],
+    "proficiencies": [ { "proficiency": "prof_metalworking" } ],
     "qualities": [ { "id": "HAMMER", "level": 2 }, { "id": "SAW_M", "level": 2 }, { "id": "DRILL", "level": 1 } ]
   },
   {