diff --git a/src/main/java/pl/inpost/webhook/router/signature/HMACSignatureVerifierExample.java b/src/main/java/pl/inpost/webhook/router/signature/HMACSignatureVerifierExample.java
index e39a39f..0376aa7 100644
--- a/src/main/java/pl/inpost/webhook/router/signature/HMACSignatureVerifierExample.java
+++ b/src/main/java/pl/inpost/webhook/router/signature/HMACSignatureVerifierExample.java
@@ -18,7 +18,7 @@ public class HMACSignatureVerifierExample {
 
   public HMACSignatureVerifierExample() {
     this.algorithm = "HmacSHA256";
-    this.key = "this is example of the HMAC key";
+    this.key = "this is an example of the HMAC key";
   }
 
   public boolean verifySignature(String body, String signatureFromXInPostSignatureHeader) {