diff --git a/src/index.test.ts b/src/index.test.ts
index 8ce97b2..5b3d9b8 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -173,6 +173,76 @@ describe("parseDocumentStoreResults", () => {
     ];
     expect(parseDocumentStoreResults(sampleRecord, true)).toStrictEqual([]);
   });
+
+  test("it should accept any numeric netId (e.g. Mantle mainnet 5000)", () => {
+    const addr = "0x2f60375e8144e16Adf1979936301D8341D58C36C";
+    const sampleRecord = [
+      {
+        name: "example.example.com.",
+        type: 16,
+        TTL: 110,
+        data: `"openatts net=ethereum netId=5000 addr=${addr}"`,
+        dnssec: false,
+      },
+    ];
+    expect(parseDocumentStoreResults(sampleRecord, false)).toStrictEqual([
+      {
+        type: "openatts",
+        net: "ethereum",
+        netId: "5000",
+        addr,
+        dnssec: false,
+      },
+    ]);
+  });
+
+  test("it should accept an arbitrary previously-unknown numeric netId", () => {
+    const addr = "0x2f60375e8144e16Adf1979936301D8341D58C36C";
+    const sampleRecord = [
+      {
+        name: "example.example.com.",
+        type: 16,
+        TTL: 110,
+        data: `"openatts net=ethereum netId=99999 addr=${addr}"`,
+        dnssec: false,
+      },
+    ];
+    expect(parseDocumentStoreResults(sampleRecord, false)).toStrictEqual([
+      {
+        type: "openatts",
+        net: "ethereum",
+        netId: "99999",
+        addr,
+        dnssec: false,
+      },
+    ]);
+  });
+
+  test("it should reject a non-numeric netId", () => {
+    const sampleRecord = [
+      {
+        name: "example.example.com.",
+        type: 16,
+        TTL: 110,
+        data: '"openatts net=ethereum netId=abc addr=0x2f60375e8144e16Adf1979936301D8341D58C36C"',
+        dnssec: false,
+      },
+    ];
+    expect(parseDocumentStoreResults(sampleRecord, false)).toStrictEqual([]);
+  });
+
+  test("it should reject an alphanumeric netId", () => {
+    const sampleRecord = [
+      {
+        name: "example.example.com.",
+        type: 16,
+        TTL: 110,
+        data: '"openatts net=ethereum netId=1abc addr=0x2f60375e8144e16Adf1979936301D8341D58C36C"',
+        dnssec: false,
+      },
+    ];
+    expect(parseDocumentStoreResults(sampleRecord, false)).toStrictEqual([]);
+  });
 });
 
 describe("queryDns", () => {
diff --git a/src/records/dnsTxt.ts b/src/records/dnsTxt.ts
index 2427ec8..a8c4989 100644
--- a/src/records/dnsTxt.ts
+++ b/src/records/dnsTxt.ts
@@ -1,4 +1,4 @@
-import { Static, Boolean, String, Literal, Record, Union, Partial } from "runtypes";
+import { Static, Boolean, String, Literal, Record, Partial } from "runtypes";
 
 export const RecordTypesT = Literal("openatts");
 
@@ -8,38 +8,8 @@ export const EthereumAddressT = String.withConstraint((maybeAddress: string) =>
   return /0x[a-fA-F0-9]{40}/.test(maybeAddress) || `${maybeAddress} is not a valid ethereum address`;
 });
 
-export enum EthereumNetworks {
-  homestead = "1",
-  ropsten = "3",
-  rinkeby = "4",
-  goerli = "5",
-  sepolia = "11155111",
-  polygon = "137",
-  polygonAmoy = "80002",
-  local = "1337",
-  xdc = "50",
-  xdcapothem = "51",
-  stabilityTestnet = "20180427",
-  stability = "101010",
-  astronTestnet = "21002",
-  astron = "1338",
-}
-
-export const EthereumNetworkIdT = Union(
-  Literal(EthereumNetworks.homestead),
-  Literal(EthereumNetworks.ropsten),
-  Literal(EthereumNetworks.rinkeby),
-  Literal(EthereumNetworks.goerli),
-  Literal(EthereumNetworks.sepolia),
-  Literal(EthereumNetworks.polygon),
-  Literal(EthereumNetworks.polygonAmoy),
-  Literal(EthereumNetworks.xdc),
-  Literal(EthereumNetworks.xdcapothem),
-  Literal(EthereumNetworks.stabilityTestnet),
-  Literal(EthereumNetworks.stability),
-  Literal(EthereumNetworks.local),
-  Literal(EthereumNetworks.astronTestnet),
-  Literal(EthereumNetworks.astron)
+export const EthereumNetworkIdT = String.withConstraint(
+  (maybeNetId: string) => /^\d+$/.test(maybeNetId) || `${maybeNetId} is not a valid numeric network id`
 );
 
 export const OpenAttestationDNSTextRecordT = Record({