diff --git a/src/main/java/tech/brenoepic/at4j/util/rest/RestRequest.java b/src/main/java/tech/brenoepic/at4j/util/rest/RestRequest.java
index 0cf6644..09d0895 100644
--- a/src/main/java/tech/brenoepic/at4j/util/rest/RestRequest.java
+++ b/src/main/java/tech/brenoepic/at4j/util/rest/RestRequest.java
@@ -104,7 +104,7 @@ public Multimap<String, String> getQueryParameters() {
    * @return An array with all used url parameters.
    */
   public String[] getUrlParameters() {
-    return urlParameters;
+    return urlParameters.clone();
   }
 
   /**
diff --git a/src/main/java/tech/brenoepic/at4j/util/rest/RestRequestInformationImpl.java b/src/main/java/tech/brenoepic/at4j/util/rest/RestRequestInformationImpl.java
index 60312c1..0cb774e 100644
--- a/src/main/java/tech/brenoepic/at4j/util/rest/RestRequestInformationImpl.java
+++ b/src/main/java/tech/brenoepic/at4j/util/rest/RestRequestInformationImpl.java
@@ -4,6 +4,7 @@
 import com.google.common.collect.Multimaps;
 import java.net.URL;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
 import tech.brenoepic.at4j.AzureApi;
@@ -35,7 +36,7 @@ public RestRequestInformationImpl(
     this.api = api;
     this.url = url;
     this.queryParameters = queryParameter;
-    this.headers = headers;
+    this.headers = new HashMap<>(headers);
     this.body = body;
   }