diff --git a/wise-webapp/src/main/java/com/wisemapping/exporter/VerticalPositionComparator.java b/wise-webapp/src/main/java/com/wisemapping/exporter/VerticalPositionComparator.java
index ccac4dd2..dfda0adc 100644
--- a/wise-webapp/src/main/java/com/wisemapping/exporter/VerticalPositionComparator.java
+++ b/wise-webapp/src/main/java/com/wisemapping/exporter/VerticalPositionComparator.java
@@ -10,9 +10,17 @@ public class VerticalPositionComparator implements Comparator<TopicType> {
     public int compare(TopicType o1, TopicType o2) {
         final String myPosition = o1.getPosition();
         final String otherPosition = o2.getPosition();
-        int myPositionY = Integer.parseInt(myPosition.split(",")[1]);
-        int otherPositionY = Integer.parseInt(otherPosition.split(",")[1]);
-        return myPositionY - otherPositionY;
+        int result;
+        if (otherPosition == null) {
+            result = -1;
+        } else if (myPosition == null) {
+            result = 1;
+        } else {
+            int myPositionY = Integer.parseInt(myPosition.split(",")[1]);
+            int otherPositionY = Integer.parseInt(otherPosition.split(",")[1]);
+            result = myPositionY - otherPositionY;
+        }
+        return result;
     }
 
 }