Added const as an extensible layer
diff --git a/CHANGES b/CHANGES
index c7c5bbb..33e06bc 100644
--- a/CHANGES
+++ b/CHANGES
@@ -7,6 +7,7 @@
 	- [bugfix] Corrected small bug where null warnings where
 	  returned in JSON (diewald)
 	- [cleanup] Converted error to failure (diewald)
+	- [bugfix] Added const layer rewrite (diewald)
 
 0.48 2014-11-07
         - [feature] Retrieval of token lists (diewald)
diff --git a/src/main/java/de/ids_mannheim/korap/KorapQuery.java b/src/main/java/de/ids_mannheim/korap/KorapQuery.java
index d07c100..70267c1 100644
--- a/src/main/java/de/ids_mannheim/korap/KorapQuery.java
+++ b/src/main/java/de/ids_mannheim/korap/KorapQuery.java
@@ -660,6 +660,10 @@
 	    case "orth":
 		layer = "s";
 		break;
+
+	    case "const":
+		layer = "c";
+		break;
 	    };
 
 	    if (isCaseInsensitive && isTerm) {
diff --git a/src/test/java/de/ids_mannheim/korap/query/TestKorapQueryJSON.java b/src/test/java/de/ids_mannheim/korap/query/TestKorapQueryJSON.java
index 32109cd..4474b10 100644
--- a/src/test/java/de/ids_mannheim/korap/query/TestKorapQueryJSON.java
+++ b/src/test/java/de/ids_mannheim/korap/query/TestKorapQueryJSON.java
@@ -301,8 +301,6 @@
 	assertEquals(sqwi.toQuery().toString(), "tokens:i:baum");
     };
 
-
-
     @Test
     public void queryJSONunderspecifiedTokenBug () {
 	// ((MORPH(APPR) ODER MORPH(APPRART)) /+w1 Urlaub
@@ -315,6 +313,12 @@
 	};
     };
 
+    @Test
+    public void queryJSONspecialLayerBug () throws QueryException {
+	SpanQueryWrapper sqwi = jsonQuery(getClass().getResource("/queries/bugs/special_layer.jsonld").getFile());
+	assertEquals(sqwi.toQuery().toString(), "spanNext(spanNext(spanNext(tokens:s:Baum, tokens:cnx/p:CC), tokens:tt/l:Baum), <tokens:xip/c:MC />)");
+    };
+
 
     @Test
     public void queryJSONrepetitionGroupRewriteBug () throws QueryException {
diff --git a/src/test/resources/queries/bugs/special_layer.jsonld b/src/test/resources/queries/bugs/special_layer.jsonld
new file mode 100644
index 0000000..92c03b0
--- /dev/null
+++ b/src/test/resources/queries/bugs/special_layer.jsonld
@@ -0,0 +1,45 @@
+{
+  "@context": "http://ids-mannheim.de/ns/KorAP/json-ld/v0.1/context.jsonld",
+  "query":{
+    "@type" : "korap:group",
+    "operands" : [
+      {
+        "@type" : "korap:token",
+        "wrap" : {
+          "@type" : "korap:term",
+          "foundry" : "opennlp",
+          "key" : "Baum",
+          "layer" : "orth",
+          "match" : "match:eq"
+        }
+      },
+      {
+        "@type" : "korap:token",
+        "wrap" : {
+          "@type" : "korap:term",
+          "foundry" : "cnx",
+          "key" : "CC",
+          "layer" : "pos",
+          "match" : "match:eq"
+        }
+      },
+      {
+        "@type" : "korap:token",
+        "wrap" : {
+          "@type" : "korap:term",
+          "foundry" : "tt",
+          "key" : "Baum",
+          "layer" : "lemma",
+          "match" : "match:eq"
+        }
+      },
+      {
+        "@type" : "korap:span",
+        "foundry" : "xip",
+        "key" : "MC",
+        "layer" : "const"
+      }
+    ],
+    "operation" : "operation:sequence"
+  }
+}