diff --git a/source/java/org/alfresco/repo/web/scripts/invite/InviteResponse.java b/source/java/org/alfresco/repo/web/scripts/invite/InviteResponse.java
index 4f28205cf6..c3d8a230fe 100644
--- a/source/java/org/alfresco/repo/web/scripts/invite/InviteResponse.java
+++ b/source/java/org/alfresco/repo/web/scripts/invite/InviteResponse.java
@@ -134,6 +134,9 @@ public class InviteResponse extends DeclarativeWebScript
         String inviteId = req.getServiceMatch().getTemplateVars().get("inviteId");
         String inviteTicket = req.getServiceMatch().getTemplateVars().get("inviteTicket");
                
+        // Check that the task is still open.
+        //if(inviteStart)
+        
         // process response
         String action = req.getServiceMatch().getTemplateVars().get("action");
         if (action.equals("accept"))
@@ -149,6 +152,10 @@ public class InviteResponse extends DeclarativeWebScript
             {
         		throw new WebScriptException(Status.STATUS_FORBIDDEN, fe.toString());            
             }
+            catch (InvitationExceptionUserError fe)
+            {
+                throw new WebScriptException(Status.STATUS_CONFLICT, fe.toString());            
+            }
         }
         else if (action.equals("reject"))
         {
@@ -162,7 +169,11 @@ public class InviteResponse extends DeclarativeWebScript
             catch (InvitationExceptionForbidden fe)
             {
         		throw new WebScriptException(Status.STATUS_FORBIDDEN, fe.toString());            
-            }  
+            }
+            catch (InvitationExceptionUserError fe)
+            {
+                throw new WebScriptException(Status.STATUS_CONFLICT, fe.toString());            
+            }
         }
         else
         {
diff --git a/source/java/org/alfresco/repo/web/scripts/invite/InviteServiceTest.java b/source/java/org/alfresco/repo/web/scripts/invite/InviteServiceTest.java
index 80ab34ba89..7e574c75ff 100644
--- a/source/java/org/alfresco/repo/web/scripts/invite/InviteServiceTest.java
+++ b/source/java/org/alfresco/repo/web/scripts/invite/InviteServiceTest.java
@@ -582,6 +582,13 @@ public class InviteServiceTest extends BaseWebScriptTest
         // Invitee accepts invitation to a Site from Inviter
         String acceptInviteUrl = URL_INVITE + "/" + inviteId + "/" + inviteTicket + "/accept";
         sendRequest(new PutRequest(acceptInviteUrl, (byte[])null, null), Status.STATUS_OK);
+        
+        // Invitee attempts to accept the invitation again
+        sendRequest(new PutRequest(acceptInviteUrl, (byte[])null, null), Status.STATUS_CONFLICT);
+        
+        // Invitee attempts to reject an invitation that has already been accepted.
+        rejectInvite(inviteId, inviteTicket, Status.STATUS_CONFLICT);
+
 
         //
         // test that invitation represented by invite ID (of invitation started
@@ -610,6 +617,9 @@ public class InviteServiceTest extends BaseWebScriptTest
         String inviteTicket = result.getString("inviteTicket");
 
         rejectInvite(inviteId, inviteTicket, Status.STATUS_OK);
+        
+        // Negative test 
+        rejectInvite(inviteId, inviteTicket, Status.STATUS_CONFLICT);
 
         //
         // test that invite represented by invite ID (of invitation started
@@ -624,6 +634,8 @@ public class InviteServiceTest extends BaseWebScriptTest
 
         // there should no longer be any invites identified by invite ID pending
         // assertEquals(0, getInvitesResult.getJSONArray("invites").length());
+        
+        
     }
 
     public void testGetInvitesByInviteId() throws Exception