diff --git a/src/main/java/org/gcube/portal/invites/InvitesManager.java b/src/main/java/org/gcube/portal/invites/InvitesManager.java
index b2c6ac3..de93cb1 100644
--- a/src/main/java/org/gcube/portal/invites/InvitesManager.java
+++ b/src/main/java/org/gcube/portal/invites/InvitesManager.java
@@ -1,5 +1,6 @@
 package org.gcube.portal.invites;
 
+import java.net.URLEncoder;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.List;
@@ -118,13 +119,15 @@ public class InvitesManager {
 
 			long groupId = PortalContext.getConfiguration().getCurrentGroupId(request);
 
-			StringBuilder getParamsEncoded = new StringBuilder(new String(Base64.encodeBase64(INVITEID_ATTR.getBytes())))
+		;
+			
+			StringBuilder getParamsEncoded = new StringBuilder(URLEncoder.encode(new String(Base64.encodeBase64(INVITEID_ATTR.getBytes())), "UTF-8"))
 					.append("=")
-					.append(new String(Base64.encodeBase64(invite.getKey().getBytes())))
+					.append(URLEncoder.encode(new String(Base64.encodeBase64(invite.getKey().getBytes())), "UTF-8"))
 					.append("&")
-					.append(new String(Base64.encodeBase64(SITEID_ATTR.getBytes())))
+					.append(URLEncoder.encode(new String(Base64.encodeBase64(SITEID_ATTR.getBytes())), "UTF-8"))
 					.append("=")
-					.append(new String(Base64.encodeBase64((""+groupId).getBytes())));
+					.append(URLEncoder.encode(new String(Base64.encodeBase64((""+groupId).getBytes())), "UTF-8"));
 
 			StringBuilder linkToAcceptInvite = new StringBuilder(gatewayURL)
 					.append("/")