diff --git a/src/main/java/de/ids_mannheim/korap/query/spans/UnorderedDistanceSpans.java b/src/main/java/de/ids_mannheim/korap/query/spans/UnorderedDistanceSpans.java
index 06227e2..4db9212 100644
--- a/src/main/java/de/ids_mannheim/korap/query/spans/UnorderedDistanceSpans.java
+++ b/src/main/java/de/ids_mannheim/korap/query/spans/UnorderedDistanceSpans.java
@@ -8,6 +8,8 @@
 import java.util.List;
 import java.util.Map;
 
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.TermContext;
@@ -32,7 +34,6 @@
     private long matchCost;
     protected int currentDocNum;
 
-
     /**
      * Constructs UnorderedDistanceSpans for the given
      * {@link SpanDistanceQuery} .
@@ -61,7 +62,6 @@
         hasMoreSpans = hasMoreFirstSpans && hasMoreSecondSpans;
     }
 
-
     @Override
     protected boolean advance () throws IOException {
         while (hasMoreSpans || !matchList.isEmpty()) {
@@ -69,13 +69,11 @@
                 setMatchProperties();
                 return true;
             }
-            if (prepareLists())
-                setMatchList();
+            if (prepareLists()) setMatchList();
         }
         return false;
     }
 
-
     /**
      * Updates the firstSpanList and secondSpanList by adding the next
      * possible first and second spans. Both the spans must be in the
@@ -90,7 +88,6 @@
      */
     protected abstract boolean prepareLists () throws IOException;
 
-
     /**
      * Sets the list of matches for the span having the smallest
      * position (i.e. between the first and the second spans), and its
@@ -106,16 +103,16 @@
                 hasMoreFirstSpans, secondSpanList);
         hasMoreSecondSpans = setCandidateList(secondSpanList, secondSpans,
                 hasMoreSecondSpans, firstSpanList);
-        //         System.out.println("--------------------");
-        //         System.out.println("firstSpanList:");
-        //         for (CandidateSpan cs : firstSpanList) {
-        //         System.out.println(cs.getStart() + " " + cs.getEnd());
-        //         }
-        //        
-        //         System.out.println("secondSpanList:");
-        //         for (CandidateSpan cs : secondSpanList) {
-        //         System.out.println(cs.getStart() + " " + cs.getEnd());
-        //         }
+        // System.out.println("--------------------");
+        // System.out.println("firstSpanList:");
+        // for (CandidateSpan cs : firstSpanList) {
+        // System.out.println(cs.getStart() + " " + cs.getEnd());
+        // }
+        //
+        // System.out.println("secondSpanList:");
+        // for (CandidateSpan cs : secondSpanList) {
+        // System.out.println(cs.getStart() + " " + cs.getEnd());
+        // }
 
         CandidateSpan currentFirstSpan, currentSecondSpan;
         if (!firstSpanList.isEmpty() && !secondSpanList.isEmpty()) {
@@ -126,26 +123,12 @@
             if (currentFirstSpan.getStart() < currentSecondSpan.getStart()
                     || isLastCandidateSmaller(currentFirstSpan,
                             currentSecondSpan)) {
-//                log.trace("current target: " + firstSpanList.get(0).getStart()
-//                        + " " + firstSpanList.get(0).getEnd());
-//                System.out.println("candidates:");
-//                for (CandidateSpan cs : secondSpanList) {
-//                    System.out.println(cs.getStart() + " " + cs.getEnd());
-//                }
-
                 matchList = findMatches(currentFirstSpan, secondSpanList, true);
                 updateList(firstSpanList);
             }
             else {
-//                log.trace("current target: " + secondSpanList.get(0).getStart()
-//                        + " " + secondSpanList.get(0).getEnd());
-//                System.out.println("candidates:");
-//                for (CandidateSpan cs : firstSpanList) {
-//                    System.out.println(cs.getStart() + " " + cs.getEnd());
-//                }
-
-                matchList = findMatches(currentSecondSpan, firstSpanList,
-                        false);
+                matchList =
+                        findMatches(currentSecondSpan, firstSpanList, false);
                 updateList(secondSpanList);
 
                 if (currentFirstSpan.getStart() == currentSecondSpan.getStart()
@@ -158,21 +141,14 @@
                 }
             }
         }
-        else if (firstSpanList.isEmpty()) {
-            // log.trace("current target: " + secondSpanList.get(0).getStart()
-            // + " " + secondSpanList.get(0).getEnd());
-            // log.trace("candidates: empty");
+        else if (!secondSpanList.isEmpty()) {
             updateList(secondSpanList);
         }
-        else {
-            // log.trace("current target: " + firstSpanList.get(0).getStart()
-            // + " " + firstSpanList.get(0).getEnd());
-            // log.trace("candidates: empty");
+        else if (!firstSpanList.isEmpty()) {
             updateList(firstSpanList);
         }
     }
 
-
     /**
      * Tells if the last candidate from the secondSpanList has a
      * smaller end position than the end position of the the last
@@ -189,8 +165,8 @@
     private boolean isLastCandidateSmaller (CandidateSpan currentFirstSpan,
             CandidateSpan currentSecondSpan) {
         if (currentFirstSpan.getEnd() == currentSecondSpan.getEnd()) {
-            int secondEnd = secondSpanList.get(secondSpanList.size() - 1)
-                    .getEnd();
+            int secondEnd =
+                    secondSpanList.get(secondSpanList.size() - 1).getEnd();
             int firstEnd = firstSpanList.get(firstSpanList.size() - 1).getEnd();
             return (secondEnd < firstEnd ? true : false);
         }
@@ -198,7 +174,6 @@
         return false;
     }
 
-
     /**
      * Performs an update based on the given candidateList. In
      * {@link UnorderedTokenDistanceSpans}, the first candidate in the
@@ -211,7 +186,6 @@
      */
     protected abstract void updateList (List<CandidateSpan> candidateList);
 
-
     /**
      * Sets the candidate list for the first element in the target
      * list and
@@ -236,7 +210,6 @@
             boolean hasMoreCandidates, List<CandidateSpan> targetList)
             throws IOException;
 
-
     /**
      * Finds all matches between the target span and its candidates in
      * the
@@ -254,7 +227,6 @@
     protected abstract List<CandidateSpan> findMatches (CandidateSpan target,
             List<CandidateSpan> candidateList, boolean isTargetFirstSpan);
 
-
     /**
      * Computes match properties and creates a candidate span match to
      * be added to the match list.
@@ -262,7 +234,8 @@
      * @return a candidate span match
      */
     protected CandidateSpan createMatchCandidate (CandidateSpan target,
-            CandidateSpan cs, boolean isDistanceZero, boolean isTargetFirstSpan) {
+            CandidateSpan cs, boolean isDistanceZero,
+            boolean isTargetFirstSpan) {
 
         int start = Math.min(target.getStart(), cs.getStart());
         int end = Math.max(target.getEnd(), cs.getEnd());
@@ -278,8 +251,8 @@
                 payloads.addAll(cs.getPayloads());
             }
         }
-        CandidateSpan match = new CandidateSpan(start, end, doc, cost,
-                payloads);
+        CandidateSpan match =
+                new CandidateSpan(start, end, doc, cost, payloads);
         if (isTargetFirstSpan) {
             match.setChildSpan(target);
             match.setSecondChildSpan(cs);
@@ -288,11 +261,10 @@
             match.setChildSpan(cs);
             match.setSecondChildSpan(target);
         }
-        //match.setChildSpan(cs);
+        // match.setChildSpan(cs);
         return match;
     }
 
-
     /**
      * Assigns the first candidate span in the match list as the
      * current span match, and removes it from the matchList.
@@ -311,13 +283,14 @@
 
         // log.trace("Match doc#={} start={} end={}", matchDocNumber,
         // matchStartPosition, matchEndPosition);
-        // log.trace("firstspan " + getMatchFirstSpan().getStart() + " "
+        // log.trace("firstspan " + getMatchFirstSpan().getStart() + "
+        // "
         // + getMatchFirstSpan().getEnd());
-        // log.trace("secondspan " + getMatchSecondSpan().getStart() + " "
+        // log.trace("secondspan " + getMatchSecondSpan().getStart() +
+        // " "
         // + getMatchSecondSpan().getEnd());
     }
 
-
     @Override
     public boolean skipTo (int target) throws IOException {
         if (hasMoreSpans && (secondSpans.doc() < target)) {
@@ -334,7 +307,6 @@
         return advance();
     }
 
-
     @Override
     public long cost () {
         return matchCost;
diff --git a/src/main/java/de/ids_mannheim/korap/query/spans/UnorderedElementDistanceSpans.java b/src/main/java/de/ids_mannheim/korap/query/spans/UnorderedElementDistanceSpans.java
index 388e97b..f111c29 100644
--- a/src/main/java/de/ids_mannheim/korap/query/spans/UnorderedElementDistanceSpans.java
+++ b/src/main/java/de/ids_mannheim/korap/query/spans/UnorderedElementDistanceSpans.java
@@ -6,6 +6,8 @@
 import java.util.List;
 import java.util.Map;
 
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.index.TermContext;
@@ -33,6 +35,8 @@
     // target span
     private List<CandidateSpan> elementList;
 
+    private Logger log = LogManager.getLogger(UnorderedElementDistanceSpans.class);
+    boolean DEBUG = false;
 
     /**
      * Constructs UnorderedElementDistanceSpans for the given
@@ -75,6 +79,11 @@
                         hasMoreFirstSpans);
                 hasMoreSecondSpans = addSpan(secondSpans, secondSpanList,
                         hasMoreSecondSpans);
+                
+                if (DEBUG){
+                    log.debug("prepare firstSpanList: " +firstSpanList.size());
+                    log.debug("prepare secondSpanList: " +secondSpanList.size());
+                }
             }
             else {
                 hasMoreSpans = false;
@@ -263,6 +272,7 @@
 
     @Override
     protected void updateList (List<CandidateSpan> candidateList) {
+//        if (DEBUG) log.debug("candidate list size: " +candidateList.size());
         updateElementList(candidateList.get(0).getPosition());
         candidateList.remove(0);
     }
diff --git a/src/test/java/de/ids_mannheim/korap/index/TestUnorderedElementDistanceIndex.java b/src/test/java/de/ids_mannheim/korap/index/TestUnorderedElementDistanceIndex.java
index c625818..6f3a2a5 100644
--- a/src/test/java/de/ids_mannheim/korap/index/TestUnorderedElementDistanceIndex.java
+++ b/src/test/java/de/ids_mannheim/korap/index/TestUnorderedElementDistanceIndex.java
@@ -17,6 +17,7 @@
 import de.ids_mannheim.korap.query.SpanElementQuery;
 import de.ids_mannheim.korap.query.SpanNextQuery;
 import de.ids_mannheim.korap.response.Result;
+import de.ids_mannheim.korap.util.QueryException;
 
 @RunWith(JUnit4.class)
 public class TestUnorderedElementDistanceIndex {
@@ -93,7 +94,7 @@
 
     private FieldDocument createFieldDoc5 () {
         FieldDocument fd = new FieldDocument();
-        fd.addString("ID", "doc-2");
+        fd.addString("ID", "doc-5");
         fd.addTV("base", "text",
                 "[(0-1)s:b|_1$<i>0<i>1|<>:s$<b>64<i>0<i>2<i>2<b>0|<>:p$<b>64<i>0<i>4<i>4<b>0]"
                         + "[(1-2)s:b|s:e|_2$<i>1<i>2]"
@@ -104,6 +105,20 @@
                         + "[(6-7)s:b|_7$<i>6<i>7|<>:s$<b>64<i>6<i>7<i>7<b>0|<>:p$<b>64<i>6<i>7<i>7<b>0]");
         return fd;
     }
+    
+    private FieldDocument createFieldDoc6 () {
+        FieldDocument fd = new FieldDocument();
+        fd.addString("ID", "doc-6");
+        fd.addTV("base", "text",
+                "[(0-1)s:b|_1$<i>0<i>1|<>:s$<b>64<i>0<i>2<i>2<b>0]"
+                        + "[(1-2)s:b|s:e|_2$<i>1<i>2]"
+                        + "[(2-3)s:e|_3$<i>2<i>3]"
+                        + "[(3-4)s:b|s:c|_4$<i>3<i>4]"
+                        + "[(4-5)s:a|_5$<i>4<i>5]"
+                        + "[(5-6)s:a|_6$<i>5<i>6]"
+                        + "[(6-7)s:b|_7$<i>6<i>7]");
+        return fd;
+    }
 
     public SpanQuery createQuery (String elementType, String x, String y,
             int minDistance, int maxDistance, boolean isOrdered) {
@@ -297,4 +312,21 @@
         assertEquals(4, kr.getMatch(7).startPos);
         assertEquals(7, kr.getMatch(7).endPos);
     }
+    
+    
+    /** Both candidate lists may be empty because the spans are not in an element span.
+     * 
+     * @throws IOException
+     * @throws QueryException
+     */
+    @Test
+    public void testBothCandidateListEmptyBug () throws IOException, QueryException {
+        ki = new KrillIndex();
+        ki.addDoc(createFieldDoc6());
+        ki.commit();
+
+        SpanQuery sq = createQuery("s", "s:a", "s:c", 1, 2, false);
+        kr = ki.search(sq, (short) 10);
+        assertEquals(0, kr.getMatches().size());
+    }
 }