diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/MetaQuery.java b/src/main/java/de/ids_mannheim/korap/query/serialize/MetaQuery.java
index 452d3c2..310c5e4 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/MetaQuery.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/MetaQuery.java
@@ -229,6 +229,7 @@
     public void clear() {
         this.rq.clear();
         this.mfil.clear();
+        this.mext.clear();
         this.track.clear();
     }
 
diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/PoliqarpPlusTree.java b/src/main/java/de/ids_mannheim/korap/query/serialize/PoliqarpPlusTree.java
index 422b0c3..0c45697 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/PoliqarpPlusTree.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/PoliqarpPlusTree.java
@@ -23,13 +23,17 @@
 import de.ids_mannheim.korap.query.PoliqarpPlusParser;
 import de.ids_mannheim.korap.query.serialize.AbstractSyntaxTree;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 /**
  * Map representation of Poliqarp syntax tree as returned by ANTLR
  * @author joachim
  *
  */
 public class PoliqarpPlusTree extends AbstractSyntaxTree {
-	
+
+    Logger log = LoggerFactory.getLogger(PoliqarpPlusTree.class);
 	/**
 	 * Top-level map representing the whole request.
 	 */
@@ -103,13 +107,13 @@
 	 * <br/>
 	 * The class further maintains a set of stacks which effectively keep track of which objects to embed in which containing objects. 
 	 * 
-	 * @param tree The syntax tree as returned by ANTLR
-	 * @param parser The ANTLR parser instance that generated the parse tree
+	 * @param query The syntax tree as returned by ANTLR
 	 */
 	public PoliqarpPlusTree(String query) {
 		prepareContext();
 		process(query);
 		System.out.println(">>> "+requestMap.get("query")+" <<<");
+        log.info(">>> " + requestMap.get("query") + " <<<");
 	}
 
 	private void prepareContext() {