diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4188e466..80c9b354 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,12 @@
 CHANGELOG
 =========
 
+5.1.0 (2023-08-10)
+------------------
+
+* Add `host` parameter to `Client` constructor to allow for use of the
+  Sandbox environment.
+
 5.0.0 (2023-05-16)
 ------------------
 
diff --git a/README.md b/README.md
index 54d451c0..c2fba8b3 100644
--- a/README.md
+++ b/README.md
@@ -34,6 +34,13 @@ takes your MaxMind account ID and license key. For example:
 const client = new minFraud.Client("1234", "LICENSEKEY");
 ```
 
+If you would like to use the Sandbox environment, you can 
+set the `host` parameter to `sandbox.minfraud.com`: 
+
+```js
+const client = new minFraud.Client("1234", "LICENSEKEY", 3000, 'sandbox.minfraud.com');
+```
+
 Then create a new `Transaction` object. This represents the transaction that
 you are sending to minFraud. Each transaction property is instantiated by creating
 a new instance of each property's class. For example:
diff --git a/src/webServiceClient.ts b/src/webServiceClient.ts
index 95ab3d89..ca546ed8 100644
--- a/src/webServiceClient.ts
+++ b/src/webServiceClient.ts
@@ -19,11 +19,16 @@ export default class WebServiceClient {
   private licenseKey: string;
   private timeout: number;
 
-  public constructor(accountID: string, licenseKey: string, timeout = 3000) {
+  public constructor(
+    accountID: string,
+    licenseKey: string,
+    timeout = 3000,
+    host = 'minfraud.maxmind.com'
+  ) {
     this.accountID = accountID;
     this.licenseKey = licenseKey;
     this.timeout = timeout;
-    this.host = 'minfraud.maxmind.com';
+    this.host = host;
   }
 
   public factors(transaction: Transaction): Promise<models.Factors> {