diff --git a/modules/sdk-core/src/bitgo/wallet/BuildParams.ts b/modules/sdk-core/src/bitgo/wallet/BuildParams.ts
index cc90d7a98e..530ce8a976 100644
--- a/modules/sdk-core/src/bitgo/wallet/BuildParams.ts
+++ b/modules/sdk-core/src/bitgo/wallet/BuildParams.ts
@@ -26,6 +26,9 @@ export const BuildParamsUTXO = t.partial({
   /* legacy or psbt */
   txFormat: t.unknown,
   maxChangeOutputs: t.unknown,
+  /* rbf */
+  rbfTxIds: t.array(t.string),
+  isReplaceableByFee: t.boolean,
 });
 
 export const BuildParamsStacks = t.partial({
diff --git a/modules/sdk-core/test/unit/bitgo/wallet/BuildParams.ts b/modules/sdk-core/test/unit/bitgo/wallet/BuildParams.ts
new file mode 100644
index 0000000000..926d2c5082
--- /dev/null
+++ b/modules/sdk-core/test/unit/bitgo/wallet/BuildParams.ts
@@ -0,0 +1,40 @@
+import * as assert from 'assert';
+import { BuildParams } from '../../../../src/bitgo/wallet/BuildParams';
+
+describe('BuildParams', function () {
+  it('enforces codec', function () {
+    assert.deepStrictEqual(
+      BuildParams.encode({
+        addressType: 'p2sh',
+        txFormat: 'psbt',
+        isReplaceableByFee: true,
+        recipients: [
+          {
+            amount: '10000',
+            address: '2N9Ego9KidiZR8tMP82g6RaggQtcbR9zNzH',
+          },
+        ],
+      } as any),
+      {
+        addressType: 'p2sh',
+        txFormat: 'psbt',
+        isReplaceableByFee: true,
+        recipients: [
+          {
+            amount: '10000',
+            address: '2N9Ego9KidiZR8tMP82g6RaggQtcbR9zNzH',
+          },
+        ],
+      }
+    );
+
+    assert.deepStrictEqual(
+      BuildParams.encode({
+        rbfTxIds: ['tx1'],
+      } as any),
+      {
+        rbfTxIds: ['tx1'],
+      }
+    );
+  });
+});