diff --git a/packages/caravan-clients/src/client.test.ts b/packages/caravan-clients/src/client.test.ts
index fcf4e60d20..e723b5caf0 100644
--- a/packages/caravan-clients/src/client.test.ts
+++ b/packages/caravan-clients/src/client.test.ts
@@ -125,7 +125,9 @@ describe("BlockchainClient", () => {
       type: ClientType.MEMPOOL,
       network: Network.TESTNET,
     });
-    expect(mempool.host).toEqual("https://unchained.mempool.space/testnet/api");
+    expect(mempool.host).toEqual(
+      "https://unchained.mempool.space/testnet4/api",
+    );
   });
 
   it("should set the signet host for a public client", () => {
diff --git a/packages/caravan-clients/src/client.ts b/packages/caravan-clients/src/client.ts
index 95ac4a5d04..e1fb81fcfc 100644
--- a/packages/caravan-clients/src/client.ts
+++ b/packages/caravan-clients/src/client.ts
@@ -140,6 +140,9 @@ export class BlockchainClient extends ClientBase {
     if (type !== ClientType.PRIVATE && network !== Network.MAINNET) {
       host += `/${network}`;
     }
+    if (type === ClientType.MEMPOOL && network === Network.TESTNET) {
+      host += "4";
+    }
     if (type !== ClientType.PRIVATE) {
       host += "/api";
     }