diff --git a/.gitignore b/.gitignore
index 1221a76d..6d04dcba 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,3 +10,6 @@ info
 
 # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
 hs_err_pid*
+
+# IntelliJ project files
+*.iml
diff --git a/pom.xml b/pom.xml
index ec4a1136..bc5d0420 100644
--- a/pom.xml
+++ b/pom.xml
@@ -113,6 +113,7 @@
 	  </execution>
 	</executions>
       </plugin>
+<!--
       <plugin>
 	<groupId>org.apache.maven.plugins</groupId>
 	<artifactId>maven-gpg-plugin</artifactId>
@@ -127,6 +128,7 @@
 	  </execution>
 	</executions>
       </plugin>
+-->
       <plugin>
 	<groupId>org.sonatype.plugins</groupId>
 	<artifactId>nexus-staging-maven-plugin</artifactId>
diff --git a/src/main/java/org/piwik/java/tracking/CustomVariableList.java b/src/main/java/org/piwik/java/tracking/CustomVariableList.java
index 87a7e619..260e3663 100644
--- a/src/main/java/org/piwik/java/tracking/CustomVariableList.java
+++ b/src/main/java/org/piwik/java/tracking/CustomVariableList.java
@@ -6,20 +6,19 @@
  */
 package org.piwik.java.tracking;
 
-import java.util.HashMap;
-import java.util.Iterator;
-import java.util.Map;
-import java.util.Map.Entry;
 import javax.json.Json;
 import javax.json.JsonArrayBuilder;
 import javax.json.JsonObjectBuilder;
+import java.util.Iterator;
+import java.util.Map.Entry;
+import java.util.concurrent.ConcurrentHashMap;
 
 /**
  *
  * @author brettcsorba
  */
 class CustomVariableList{
-    private final Map<Integer, CustomVariable> map = new HashMap<>();
+    private final ConcurrentHashMap<Integer, CustomVariable> map = new ConcurrentHashMap<>();
 
     void add(CustomVariable cv){
         boolean found = false;