diff --git a/src/main/java/de/ids_mannheim/korap/query/spans/ExpandedExclusionSpans.java b/src/main/java/de/ids_mannheim/korap/query/spans/ExpandedExclusionSpans.java
index 80904f2..11b6fda 100644
--- a/src/main/java/de/ids_mannheim/korap/query/spans/ExpandedExclusionSpans.java
+++ b/src/main/java/de/ids_mannheim/korap/query/spans/ExpandedExclusionSpans.java
@@ -1,6 +1,7 @@
 package de.ids_mannheim.korap.query.spans;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -22,6 +23,7 @@
 	
 	private int min, max;
 	private int direction;
+	private byte classNumber;
 	private List<CandidateSpan> candidateSpans;
 	private boolean hasMoreNotClause;
 	private Spans notClause;
@@ -45,6 +47,7 @@
 		this.min = spanExpansionQuery.getMin();
 		this.max = spanExpansionQuery.getMax();
 		this.direction = spanExpansionQuery.getDirection();
+		this.classNumber = spanExpansionQuery.getClassNumber();
 		
 		this.notClause = secondSpans;
 		this.hasMoreNotClause = notClause.next();		
@@ -167,17 +170,19 @@
 			throws IOException {
 		int counter;
 		int start, end;
-				
+		CandidateSpan cs;
 		if (direction < 0 ) { // left
 			counter = maxPos;
 			while (counter >= min){
-				start = firstSpans.start() - counter;
-				if (start > -1 ){
-					
-				end = firstSpans.end();
-				//System.out.println(start+","+end);
-				candidateSpans.add(new CandidateSpan(start, end, firstSpans.doc(), 
-						firstSpans.cost(), firstSpans.getPayload()));
+				start = Math.max(0,firstSpans.start() - counter);
+				if (start > -1 ){					
+					end = firstSpans.end();
+					//System.out.println(start+","+end);
+					cs = new CandidateSpan(start, end, firstSpans.doc(),
+							firstSpans.cost(), 
+							calculatePayload(start,firstSpans.start())
+					);
+					candidateSpans.add(cs);
 				}
 				counter --;
 			}
@@ -188,13 +193,39 @@
 				start = firstSpans.start();
 				end = firstSpans.end() + counter;
 				//System.out.println(start+","+end);
-				candidateSpans.add(new CandidateSpan(start, end, firstSpans.doc(), 
-						firstSpans.cost(), firstSpans.getPayload()));
+				
+				cs = new CandidateSpan(start, end, firstSpans.doc(), 
+						firstSpans.cost(), 
+						calculatePayload(firstSpans.end(), end)
+				);				
+				candidateSpans.add(cs);
 				counter++;
 			}			
 		}
 	}
 	
+	private ArrayList<byte[]> calculatePayload(int start, int end)
+			throws IOException{
+		
+		ArrayList<byte[]> payload = new ArrayList<byte[]>();
+									
+		if (firstSpans.isPayloadAvailable()){				
+			payload.addAll(firstSpans.getPayload());
+		}
+		if (classNumber > 0 ){	
+			System.out.println("Extension offsets "+start+","+end);
+			payload.add(calculateExtensionOffsets(start, end));
+		}
+		return payload;
+	}
+	
+	private byte[] calculateExtensionOffsets(int start, int end) {
+		ByteBuffer buffer = ByteBuffer.allocate(9);
+		buffer.put(classNumber);
+		buffer.putInt(start);					
+		buffer.putInt(end);					
+		return buffer.array();
+	}
 	
 	@Override
 	public boolean skipTo(int target) throws IOException {
diff --git a/src/test/java/de/ids_mannheim/korap/index/TestSpanExpansionIndex.java b/src/test/java/de/ids_mannheim/korap/index/TestSpanExpansionIndex.java
index 3acfc8a..a4df2d6 100644
--- a/src/test/java/de/ids_mannheim/korap/index/TestSpanExpansionIndex.java
+++ b/src/test/java/de/ids_mannheim/korap/index/TestSpanExpansionIndex.java
@@ -65,22 +65,46 @@
 	}
 	
 	/** Classnumber
-	 * 	Cannot check the correctness directly
+	 * 	Cannot check the expansion offset correctness directly
 	 * */
 	@Test
 	public void testCase2() {
 		byte classNumber = 1;
-		
+		SpanExpansionQuery sq;
 		// create new payload for the expansion offsets
 		SpanTermQuery stq = new SpanTermQuery(new Term("tokens","s:Kaiser")	);
-		SpanExpansionQuery sq = new SpanExpansionQuery(stq, 0, 2, -1, classNumber, true);		
+		sq = new SpanExpansionQuery(stq, 0, 2, -1, classNumber, true);		
 		kr = ki.search(sq, (short) 10);
-				
+		
+		assertEquals(5, kr.getMatch(0).getStartPos());	// expansion 5,7
+        assertEquals(8, kr.getMatch(0).getEndPos());	
+        assertEquals(6, kr.getMatch(1).getStartPos());	// expansion 6,9
+        assertEquals(8, kr.getMatch(1).getEndPos());        
+        assertEquals(7, kr.getMatch(2).getStartPos()); 	// expansion 7,7
+        assertEquals(8, kr.getMatch(2).getEndPos());	
+        assertEquals(13, kr.getMatch(3).getStartPos());	// expansion 13,15
+        assertEquals(16, kr.getMatch(3).getEndPos());	 
+		
+		/*for (KorapMatch km : kr.getMatches()){		
+			System.out.println(km.getStartPos() +","+km.getEndPos()+" "
+				+km.getSnippetBrackets());
+		}*/
+		
 		// add expansion offsets to the existing payload
 		SpanElementQuery seq = new SpanElementQuery("tokens", "cnx/c:np");
 		sq = new SpanExpansionQuery(seq, 1, 2, 0, classNumber, true);		
 		kr = ki.search(sq, (short) 10);
 		
+		assertEquals(1, kr.getMatch(0).getStartPos());
+        assertEquals(3, kr.getMatch(0).getEndPos());
+        assertEquals(1, kr.getMatch(1).getStartPos());
+        assertEquals(4, kr.getMatch(1).getEndPos());        
+        assertEquals(6, kr.getMatch(2).getStartPos()); 	// expansion 8,9
+        assertEquals(9, kr.getMatch(2).getEndPos());	
+        assertEquals(6, kr.getMatch(3).getStartPos());	// expansion 8,10
+        assertEquals(10, kr.getMatch(3).getEndPos());	 
+        
+        
 		/*for (KorapMatch km : kr.getMatches()){		
 			System.out.println(km.getStartPos() +","+km.getEndPos()+" "
 				+km.getSnippetBrackets());
@@ -88,40 +112,60 @@
 	}
 	
 	
-	/** Expansion with exclusion
+	/** Right expansion with exclusion
 	 * */
 	@Test
 	public void testCase3() throws IOException {
-		
+		byte classNumber = 1;
 		SpanTermQuery stq = new SpanTermQuery(new Term("tokens","cnx/p:N")	);
 		SpanTermQuery notQuery = new SpanTermQuery(new Term("tokens","s:September"));
 		
-		SpanExpansionQuery seq = new SpanExpansionQuery(stq, notQuery, 2, 3, 0, true);		
+		SpanExpansionQuery seq = new SpanExpansionQuery(stq, notQuery, 2, 3, 0, 
+				classNumber, true);		
 		kr = ki.search(seq, (short) 20);
 		
+		assertEquals(13, kr.getMatch(11).getStartPos());	// expansion 14,17
+        assertEquals(17, kr.getMatch(11).getEndPos());	 
+		assertEquals(18, kr.getMatch(12).getStartPos());	// expansion 19,21
+        assertEquals(21, kr.getMatch(12).getEndPos());
+        assertEquals(18, kr.getMatch(13).getStartPos());	// expansion 19,22
+        assertEquals(22, kr.getMatch(13).getEndPos());        
+        assertEquals(20, kr.getMatch(14).getStartPos()); 	// expansion 21,23
+        assertEquals(23, kr.getMatch(14).getEndPos());	
+        		
 		/*for (KorapMatch km : kr.getMatches()){
 			System.out.println(km.getStartPos() +","+km.getEndPos()+" "
 					+km.getSnippetBrackets());
 		}*/
 	}
 	
-	/** Expansion with exclusion
+	/** Left expansion with exclusion
 	 * */
 	@Test
 	public void testCase4() throws IOException {
-		
+		byte classNumber = 1;
 		SpanTermQuery stq = new SpanTermQuery(new Term("tokens","cnx/p:N")	);
 		SpanTermQuery notQuery = new SpanTermQuery(new Term("tokens","cnx/p:A"));
 		
-		SpanExpansionQuery seq = new SpanExpansionQuery(stq, notQuery, 0, 2, -1, true);		
+		SpanExpansionQuery seq = new SpanExpansionQuery(stq, notQuery, 0, 2, -1, 
+				classNumber, true);		
 		kr = ki.search(seq, (short) 10);
 
-		/*
+		assertEquals(7, kr.getMatch(3).getStartPos());	// expansion 7,7
+        assertEquals(8, kr.getMatch(3).getEndPos());
+        assertEquals(7, kr.getMatch(4).getStartPos());	// expansion 7,8
+        assertEquals(9, kr.getMatch(4).getEndPos());        
+        assertEquals(8, kr.getMatch(5).getStartPos()); 	// expansion 8,8 // no expansion // no need???
+        assertEquals(9, kr.getMatch(5).getEndPos());	
+        assertEquals(8, kr.getMatch(6).getStartPos());	// expansion 8,10
+        assertEquals(11, kr.getMatch(6).getEndPos());	 
+		
+		
 		for (KorapMatch km : kr.getMatches()){
 			System.out.println(km.getStartPos() +","+km.getEndPos()+" "
 					+km.getSnippetBrackets());
 		}
-		*/
+		
 	}
 	
 }