diff --git a/src/main/java/de/ids_mannheim/korap/query/spans/FocusSpans.java b/src/main/java/de/ids_mannheim/korap/query/spans/FocusSpans.java
index c694f26..6a7d8c4 100644
--- a/src/main/java/de/ids_mannheim/korap/query/spans/FocusSpans.java
+++ b/src/main/java/de/ids_mannheim/korap/query/spans/FocusSpans.java
@@ -107,6 +107,7 @@
         CandidateSpan cs;
 
         if (DEBUG) {
+            log.debug("FirstSpan [{}]", firstSpans.toString());
             log.debug("FirstSpan: ({}) {}-{}", firstSpans.doc(), firstSpans.start(), firstSpans.end());
         }
         
diff --git a/src/main/java/de/ids_mannheim/korap/query/spans/NextSpans.java b/src/main/java/de/ids_mannheim/korap/query/spans/NextSpans.java
index 1068e58..466548e 100644
--- a/src/main/java/de/ids_mannheim/korap/query/spans/NextSpans.java
+++ b/src/main/java/de/ids_mannheim/korap/query/spans/NextSpans.java
@@ -156,6 +156,9 @@
                               firstSpans.doc(),
                               secondSpans.doc()
                         );
+                    log.debug("First span [{}]",firstSpans.toString());
+                    log.debug("Second span [{}]",secondSpans.toString());
+
                 }
                 candidateListDocNum = firstSpans.doc();
                 searchMatches();
@@ -267,7 +270,11 @@
             if (!firstSpans.skipTo(target)) {
                 hasMoreSpans = false;
                 return false;
-            };
+            }
+            else {
+                // removed all matches found in the previous doc.
+                matchList.clear();
+            }
 
             if (DEBUG) {
                 log.debug("Skip firstSpans to {}={} succeed with positions {}-{}",