diff --git a/src/clob/types/response.rs b/src/clob/types/response.rs
index 2dbd1785..b168e0db 100644
--- a/src/clob/types/response.rs
+++ b/src/clob/types/response.rs
@@ -653,8 +653,8 @@ pub struct BuilderTradeResponse {
     pub trade_type: String,
     /// Hash of the taker order.
     pub taker_order_hash: B256,
-    /// Address of the builder.
-    pub builder: Address,
+    /// Builder API key ID.
+    pub builder: ApiKey,
     /// The market condition ID.
     pub market: B256,
     pub asset_id: U256,
diff --git a/tests/clob.rs b/tests/clob.rs
index f4bacadb..6b30d18a 100644
--- a/tests/clob.rs
+++ b/tests/clob.rs
@@ -3157,7 +3157,7 @@ mod builder_authenticated {
                         "id": "1",
                         "tradeType": "limit",
                         "takerOrderHash": "0x0000000000000000000000000000000000000000000000000074616b65726f72",
-                        "builder": "0x00000000000000000000000000006275696c6431",
+                        "builder": "019b618b-4a91-7dd9-a4c9-aadfbcbd5b95",
                         "market": "0x000000000000000000000000000000000000000000000000000000006d61726b",
                         "assetId": token_1(),
                         "side": "buy",
@@ -3199,7 +3199,7 @@ mod builder_authenticated {
             .taker_order_hash(b256!(
                 "0000000000000000000000000000000000000000000000000074616b65726f72"
             ))
-            .builder(address!("00000000000000000000000000006275696c6431"))
+            .builder(Uuid::parse_str("019b618b-4a91-7dd9-a4c9-aadfbcbd5b95").unwrap())
             .market(b256!(
                 "000000000000000000000000000000000000000000000000000000006d61726b"
             ))