diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/rest/Access.java b/src/main/java/org/gcube/informationsystem/resourceregistry/rest/Access.java
index ef9561a..6738966 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/rest/Access.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/rest/Access.java
@@ -245,7 +245,9 @@ public class Access {
 		
 		Map<String, String> constraint = new HashMap<>();
 		for(String key : multivaluedMap.keySet()){
-			constraint.put(key, multivaluedMap.getFirst(key));
+			if(key.compareTo(AccessPath.POLYMORPHIC_PARAM)!=0){
+				constraint.put(key, multivaluedMap.getFirst(key));
+			}
 		}
 		constraint.put(AccessPath.RELATION_TYPE_PATH_PART, relationType);
 		constraint.put(AccessPath.FACET_TYPE_PATH_PART, facetType);