diff --git a/src/main/java/de/ids_mannheim/korap/query/parse/fcsql/ExpressionParser.java b/src/main/java/de/ids_mannheim/korap/query/parse/fcsql/ExpressionParser.java
index 5d767a9..1dc4a4b 100644
--- a/src/main/java/de/ids_mannheim/korap/query/parse/fcsql/ExpressionParser.java
+++ b/src/main/java/de/ids_mannheim/korap/query/parse/fcsql/ExpressionParser.java
@@ -64,7 +64,8 @@
         //
         // }
         else if (queryNode instanceof ExpressionNot) {
-            return parseExpression(queryNode.getChild(0), true, true);
+            boolean negation = isNot ? false : true;
+            return parseExpression(queryNode.getChild(0), negation, isToken);
         }
         else if (queryNode instanceof ExpressionOr) {
             List<QueryNode> operands = queryNode.getChildren();
diff --git a/src/main/java/de/ids_mannheim/korap/query/parse/fcsql/FCSSRUQueryParser.java b/src/main/java/de/ids_mannheim/korap/query/parse/fcsql/FCSSRUQueryParser.java
index a98cc6e..ba440a3 100644
--- a/src/main/java/de/ids_mannheim/korap/query/parse/fcsql/FCSSRUQueryParser.java
+++ b/src/main/java/de/ids_mannheim/korap/query/parse/fcsql/FCSSRUQueryParser.java
@@ -8,6 +8,7 @@
 import de.ids_mannheim.korap.query.serialize.FCSQLQueryProcessor;
 import de.ids_mannheim.korap.query.serialize.util.StatusCodes;
 import eu.clarin.sru.server.fcs.parser.QueryDisjunction;
+import eu.clarin.sru.server.fcs.parser.QueryGroup;
 import eu.clarin.sru.server.fcs.parser.QueryNode;
 import eu.clarin.sru.server.fcs.parser.QuerySegment;
 import eu.clarin.sru.server.fcs.parser.QuerySequence;
@@ -26,8 +27,9 @@
 
         if (queryNode instanceof QuerySegment) {
             return parseQuerySegment((QuerySegment) queryNode);
-            // } else if (queryNode instanceof QueryGroup) {
-            //
+        }
+        else if (queryNode instanceof QueryGroup) {
+            return parseQueryNode(queryNode.getChild(0));
         }
         else if (queryNode instanceof QuerySequence) {
             return parseGroupQuery(queryNode.getChildren(),
diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/FCSQLQueryProcessor.java b/src/main/java/de/ids_mannheim/korap/query/serialize/FCSQLQueryProcessor.java
index 3862664..1e973d8 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/FCSQLQueryProcessor.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/FCSQLQueryProcessor.java
@@ -56,8 +56,10 @@
     public void process(String query) {
         if (isVersionValid()) {
             FCSSRUQuery fcsSruQuery = parseQueryStringtoFCSQuery(query);
-            QueryNode fcsQueryNode = fcsSruQuery.getParsedQuery();
-            parseFCSQueryToKoralQuery(fcsQueryNode);
+            if (fcsSruQuery != null) {
+                QueryNode fcsQueryNode = fcsSruQuery.getParsedQuery();
+                parseFCSQueryToKoralQuery(fcsQueryNode);
+            }
         }
     }
 
@@ -83,13 +85,19 @@
         try {
             QueryNode parsedQuery = fcsParser.parse(query);
             fcsQuery = new FCSSRUQuery(query, parsedQuery);
+            if (fcsQuery == null) {
+                addError(StatusCodes.UNKNOWN_QUERY_ERROR,
+                        "FCS diagnostic 10: Unexpected error while parsing query.");
+            }
         }
         catch (QueryParserException e) {
-            addError(StatusCodes.UNKNOWN_QUERY_ERROR, "FCS diagnostic 10: +"
-                    + e.getMessage());
+            addError(
+                    StatusCodes.UNKNOWN_QUERY_ERROR,
+                    "FCS diagnostic 10: Query cannot be parsed, "
+                            + e.getMessage());
         }
         catch (Exception e) {
-            addError(StatusCodes.UNKNOWN_QUERY_ERROR, "FCS diagnostic 10: +"
+            addError(StatusCodes.UNKNOWN_QUERY_ERROR, "FCS diagnostic 10: "
                     + "Unexpected error while parsing query.");
         }
         return fcsQuery;