diff --git a/src/assetId.ts b/src/assetId.ts
index 1cf3a4a..9ce641d 100644
--- a/src/assetId.ts
+++ b/src/assetId.ts
@@ -12,7 +12,7 @@ export interface AssetIdParams {
 }
 
 export class AssetId {
-  public static spec: IdentifierSpec = CAIP["19"].assetId;
+  public static spec: IdentifierSpec = CAIP["19"].blockNumberTag;
 
   public static parse(id: string): AssetIdParams {
     if (!isValidId(id, this.spec)) {
diff --git a/src/spec.ts b/src/spec.ts
index 273c02d..190b04f 100644
--- a/src/spec.ts
+++ b/src/spec.ts
@@ -87,28 +87,17 @@ const CAIP19AssetId: IdentifierSpec = {
   },
 };
 
-const BlockNumberTag: IdentifierSpec = {
-  name: "blockNumberTag",
-  regex: "[0-9]{1,78}|latest",
-  parameters: {
-    delimiter: "",
-    values: {
-      0: {
-        name: "blockNumberTag",
-        regex: "[0-9]{1,78}|latest",
-      },
-    },
-  },
-};
-
 const CAIP19BlockNumberTag: IdentifierSpec = {
   name: "blockNumberTag",
-  regex: ".*",
+  regex: "[-:a-zA-Z0-9]{13,226}",
   parameters: {
     delimiter: "#",
     values: {
       0: CAIP19AssetId,
-      2: BlockNumberTag,
+      1: {
+        name: "blockNumberTag",
+        regex: "[0-9]{1,78}|latest",
+      },
     },
   },
 };
@@ -119,6 +108,7 @@ export const CAIP = {
   "19": {
     assetName: AssetName,
     assetType: CAIP19AssetType,
-    assetId: CAIP19BlockNumberTag,
+    assetId: CAIP19AssetId,
+    blockNumberTag: CAIP19BlockNumberTag,
   },
 };
diff --git a/test/assetId.test.ts b/test/assetId.test.ts
index 2324ba3..659d29c 100644
--- a/test/assetId.test.ts
+++ b/test/assetId.test.ts
@@ -6,6 +6,7 @@ function assertInterface(result: AssetId) {
   expect(result.chainId.toString()).toEqual(data.CHAIN_ID_STRING);
   expect(result.assetName.toString()).toEqual(data.ASSET_NAME_STRING);
   expect(result.tokenId).toEqual(data.TOKEN_ID);
+  expect(result.blockNumberTag).toEqual(data.BLOCK_NUMBER_TAG);
   expect(result.toString()).toEqual(data.ASSET_ID_STRING);
   expect(result.toJSON()).toEqual(data.ASSET_ID_NESTED_PARAMS);
 }