diff --git a/pom.xml b/pom.xml
index 2f9e9d5..db97761 100644
--- a/pom.xml
+++ b/pom.xml
@@ -99,10 +99,20 @@
     <sourceDirectory>${basedir}/src/main/java</sourceDirectory>
     <outputDirectory>${basedir}/target/classes</outputDirectory>
     <plugins>
+     <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.3</version>
+                <configuration>
+                    <compilerVersion>1.7</compilerVersion>
+                    <source>1.7</source>
+                    <target>1.7</target>
+                </configuration>
+            </plugin>
       <!--
 	  Formatter plugin for Eclipse based coding conventions
 	  http://maven-java-formatter-plugin.googlecode.com/svn/site/0.4/usage.html
-      -->
+      -->      
       <plugin>
 	<groupId>com.googlecode.maven-java-formatter-plugin</groupId>
 	<artifactId>maven-java-formatter-plugin</artifactId>
diff --git a/src/test/java/de/ids_mannheim/korap/query/serialize/CollectionQueryDuplicateTest.java b/src/test/java/de/ids_mannheim/korap/query/serialize/CollectionQueryDuplicateTest.java
new file mode 100644
index 0000000..d3c1faa
--- /dev/null
+++ b/src/test/java/de/ids_mannheim/korap/query/serialize/CollectionQueryDuplicateTest.java
@@ -0,0 +1,32 @@
+package de.ids_mannheim.korap.query.serialize;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.Test;
+
+import java.io.IOException;
+
+/**
+ * @author hanl
+ * @date 28/07/2015
+ */
+public class CollectionQueryDuplicateTest {
+
+    @Test
+    public void testCollectionQueryDuplicateThrowsAssertionException() {
+        QuerySerializer serializer = new QuerySerializer();
+        serializer.setQuery("[base=Haus]", "poliqarp");
+        serializer.setCollection("textClass=politik & corpusID=WPD");
+        ObjectMapper m = new ObjectMapper();
+        try {
+            JsonNode first = m.readTree(serializer.toJSON());
+            JsonNode second = m.readTree(serializer.toJSON());
+
+            assert first.at("/collection").equals(second.at("/collection"));
+
+        }catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+}