2 files changed, 8 insertions, 2 deletions
diff --git a/packages/types/CHANGELOG.json b/packages/types/CHANGELOG.json
index 53e1f3716..106dc3281 100644
--- a/packages/types/CHANGELOG.json
+++ b/packages/types/CHANGELOG.json
@@ -9,6 +9,10 @@
             {
                 "note": "Added `ZeroExTransaction` type for Exchange executeTransaction",
                 "pr": 1102
+            },
+            {
+                "note": "Add `AssetData` union type (`type AssetData = ERC20AssetData | ERC721AssetData`)",
+                "pr": 1131
             }
         ]
     },
diff --git a/packages/types/src/index.ts b/packages/types/src/index.ts
index d33048b61..c038df50c 100644
--- a/packages/types/src/index.ts
+++ b/packages/types/src/index.ts
@@ -158,16 +158,18 @@ export enum AssetProxyId {
 }
 
 export interface ERC20AssetData {
-    assetProxyId: string;
+    assetProxyId: AssetProxyId.ERC20;
     tokenAddress: string;
 }
 
 export interface ERC721AssetData {
-    assetProxyId: string;
+    assetProxyId: AssetProxyId.ERC721;
     tokenAddress: string;
     tokenId: BigNumber;
 }
 
+export type AssetData = ERC20AssetData | ERC721AssetData;
+
 // TODO: DRY. These should be extracted from contract code.
 export enum RevertReason {
     OrderUnfillable = 'ORDER_UNFILLABLE',