diff --git a/annis-service/src/main/antlr4/annis/ql/AqlParser.g4 b/annis-service/src/main/antlr4/annis/ql/AqlParser.g4
index 12d2c42e15..8a0c67856f 100644
--- a/annis-service/src/main/antlr4/annis/ql/AqlParser.g4
+++ b/annis-service/src/main/antlr4/annis/ql/AqlParser.g4
@@ -110,6 +110,7 @@ notequalvalue
   : NEQ 
   ;
 
+
 operator
   : precedence
   | near
@@ -119,13 +120,17 @@ operator
   | commonparent
   | commonancestor
   | identity
-  | equalvalue
-  | notequalvalue
   ;
 
+/* Addtional operators that are do not bind two variables. */
+nonbinding_operator
+ : equalvalue
+ | notequalvalue
+ ;
 
 n_ary_linguistic_term
-  :  refOrNode (operator refOrNode)+ # Relation
+  :  refOrNode (operator refOrNode)+ # BindingRelation
+  | REF (nonbinding_operator REF)+ # NonBindingRelation
   ;
 
 	
diff --git a/annis-service/src/main/java/annis/ql/parser/JoinListener.java b/annis-service/src/main/java/annis/ql/parser/JoinListener.java
index f77214493a..a5a6895f79 100644
--- a/annis-service/src/main/java/annis/ql/parser/JoinListener.java
+++ b/annis-service/src/main/java/annis/ql/parser/JoinListener.java
@@ -124,9 +124,8 @@ public void exitOperator(AqlParser.OperatorContext ctx)
     relationIdx++;
   }
 
-
   @Override
-  public void enterRelation(AqlParser.RelationContext ctx)
+  public void enterBindingRelation(AqlParser.BindingRelationContext ctx)
   {
     int numOfReferences = ctx.refOrNode().size();
     relationIdx = 0;
@@ -145,6 +144,27 @@ public void enterRelation(AqlParser.RelationContext ctx)
       relationChain.add(i, n);
     }
   }
+
+  @Override
+  public void enterNonBindingRelation(AqlParser.NonBindingRelationContext ctx)
+  {
+    int numOfReferences = ctx.REF().size();
+    relationIdx = 0;
+    relationChain.clear();
+    relationChain.ensureCapacity(numOfReferences);
+    
+    for(int i=0; i < numOfReferences; i++)
+    {
+      QueryNode n = nodeByRef(ctx.REF(i).getSymbol());
+      if(n == null)
+      {
+        throw new AnnisQLSemanticsException(
+          AnnisParserAntlr.getLocation(ctx.getStart(), ctx.getStop()), 
+          "invalid reference to '" + ctx.REF(i).getText() + "'");
+      }
+      relationChain.add(i, n);
+    }
+  }
   
   @Override
   public void enterRootTerm(AqlParser.RootTermContext ctx)
diff --git a/annis-service/src/test/java/annis/ql/parser/TestAnnisParser-examples.xml b/annis-service/src/test/java/annis/ql/parser/TestAnnisParser-examples.xml
index cbf2c42d2a..6c1f0a4e64 100644
--- a/annis-service/src/test/java/annis/ql/parser/TestAnnisParser-examples.xml
+++ b/annis-service/src/test/java/annis/ql/parser/TestAnnisParser-examples.xml
@@ -87,7 +87,8 @@
     <value><![CDATA[node _ident_ node _ident_ pos="NN"]]></value>
     <value><![CDATA[pos . lemma . pos & #1 == #2]]></value>
     <value><![CDATA[pos . lemma . pos & #1 != #2]]></value>
-<!--    <value><![CDATA[ZH1Diff="INS" . tok!=""]]></value> -->
+    <!-- issue #494 -->
+    <value><![CDATA[ZH1Diff="INS" . tok!=""]]></value>
     <!-- corner cases of OR -->
     <value><![CDATA["das" | "die" | "der"]]></value>
     <value><![CDATA["das" | ("die" & pos="NN" & #2 . #3) | "der"]]></value>