diff --git a/models/MarketTradeGood.json b/models/MarketTradeGood.json
index 414454d..2f085ad 100644
--- a/models/MarketTradeGood.json
+++ b/models/MarketTradeGood.json
@@ -2,8 +2,7 @@
   "type": "object",
   "properties": {
     "symbol": {
-      "type": "string",
-      "description": "The symbol of the trade good."
+      "$ref": "./TradeSymbol.json"
     },
     "type": {
       "type": "string",
diff --git a/models/ShipCargoItem.json b/models/ShipCargoItem.json
index 052a220..af37796 100644
--- a/models/ShipCargoItem.json
+++ b/models/ShipCargoItem.json
@@ -3,8 +3,7 @@
   "description": "The type of cargo item and the number of units.",
   "properties": {
     "symbol": {
-      "type": "string",
-      "description": "The unique identifier of the cargo item type."
+      "$ref": "./TradeSymbol.json"
     },
     "name": {
       "type": "string",