diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/CollectionQueryTree.java b/src/main/java/de/ids_mannheim/korap/query/serialize/CollectionQueryTree.java
index 15a1f11..dc3405a 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/CollectionQueryTree.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/CollectionQueryTree.java
@@ -100,7 +100,10 @@
                 term.putAll(parseValue(valueNodes.get(0)));
                 String match = operatorNodes.get(0).getText();
                 term.put("match", "match:" + interpretMatch(match));
-                checkOperatorValueConformance(term);
+                if (checkOperatorValueConformance(term) == 1) {
+                	requestMap.put("query", new LinkedHashMap<String,Object>());
+                	return;
+                }
                 putIntoSuperObject(term);
             } else { // (valueNodes.size()==2)
                 LinkedHashMap<String, Object> termGroup = makeDocGroup("and");
@@ -112,7 +115,10 @@
                 String match1 = operatorNodes.get(0).getText();
                 term1.put("match", "match:" + invertInequation(interpretMatch(match1)));
                 termGroupOperands.add(term1);
-                checkOperatorValueConformance(term1);
+                if (checkOperatorValueConformance(term1) == 1) {
+                	requestMap.put("query", new LinkedHashMap<String,Object>());
+                	return;
+                }
 
                 LinkedHashMap<String, Object> term2 = makeDoc();
                 term2.put("key", field);
@@ -120,7 +126,10 @@
                 String match2 = operatorNodes.get(1).getText();
                 term2.put("match", "match:" + interpretMatch(match2));
                 termGroupOperands.add(term2);
-                checkOperatorValueConformance(term2);
+                if (checkOperatorValueConformance(term2) == 1) {
+                	requestMap.put("query", new LinkedHashMap<String,Object>());
+                	return;
+                }
 
                 putIntoSuperObject(termGroup);
             }
@@ -203,15 +212,17 @@
     }
 
 
-    private void checkOperatorValueConformance(LinkedHashMap<String, Object> term) {
+    private int checkOperatorValueConformance(LinkedHashMap<String, Object> term) {
 		String match = (String) term.get("match");
 		String type = (String) term.get("type");
 		if (type == null || type.equals("type:regex")) {
 			if (!(match.equals("match:eq") || match.equals("match:ne"))) {
 				errorMsgs.add("You used an inequation operator with a string value.");
 				System.err.println("You used an inequation operator with a string value.");
+				return 1;
 			}
 		}
+		return 0;
 	}
 
 	private LinkedHashMap<String, Object> parseValue(ParseTree valueNode) {