diff --git a/scripts-available/CDB_Groups.sql b/scripts-available/CDB_Groups.sql
index 253e72c..716032e 100644
--- a/scripts-available/CDB_Groups.sql
+++ b/scripts-available/CDB_Groups.sql
@@ -52,7 +52,7 @@ $$ LANGUAGE PLPGSQL VOLATILE;
 
 -- Adds users to a group, comma-separated
 CREATE OR REPLACE
-FUNCTION cartodb.CDB_Group_AddUsers(group_name text, usernames text)
+FUNCTION cartodb.CDB_Group_AddUsers(group_name text, usernames text[])
     RETURNS VOID AS $$
 DECLARE
     group_role TEXT;
@@ -60,7 +60,7 @@ DECLARE
     username TEXT;
 BEGIN
     group_role := cartodb._CDB_Group_GroupRole(group_name);
-    foreach username in array string_to_array(usernames, ',')
+    foreach username in array usernames
     loop
       user_role := cartodb._CDB_User_RoleFromUsername(username);
       IF(group_role IS NULL OR user_role IS NULL)
@@ -75,7 +75,7 @@ $$ LANGUAGE PLPGSQL VOLATILE;
 
 -- Removes a user from a group
 CREATE OR REPLACE
-FUNCTION cartodb.CDB_Group_RemoveUsers(group_name text, usernames text)
+FUNCTION cartodb.CDB_Group_RemoveUsers(group_name text, usernames text[])
     RETURNS VOID AS $$
 DECLARE
     group_role TEXT;
@@ -83,7 +83,7 @@ DECLARE
     username TEXT;
 BEGIN
     group_role := cartodb._CDB_Group_GroupRole(group_name);
-    foreach username in array string_to_array(usernames, ',')
+    foreach username in array usernames
     loop
       user_role := cartodb._CDB_User_RoleFromUsername(username);
       EXECUTE format('REVOKE %I FROM %I', group_role, user_role);
diff --git a/scripts-available/CDB_Groups_API.sql b/scripts-available/CDB_Groups_API.sql
index ed5447f..136a969 100644
--- a/scripts-available/CDB_Groups_API.sql
+++ b/scripts-available/CDB_Groups_API.sql
@@ -51,27 +51,27 @@ $$
 $$ LANGUAGE 'plpythonu' VOLATILE SECURITY DEFINER;
 
 CREATE OR REPLACE
-FUNCTION cartodb._CDB_Group_AddUsers_API(group_name text, usernames text)
+FUNCTION cartodb._CDB_Group_AddUsers_API(group_name text, usernames text[])
     RETURNS VOID AS
 $$
     import string
     import urllib
 
     url = '/api/v1/databases/{0}/groups/%s/users' % (urllib.pathname2url(group_name))
-    body = "{ \"users\": [\"%s\"] }" % "\",\"".join(usernames.split(','))
+    body = "{ \"users\": [\"%s\"] }" % "\",\"".join(usernames)
     query = "select cartodb._CDB_Group_API_Request('POST', '%s', '%s', '{200, 409}') as response_status" % (url, body)
     plpy.execute(query)
 $$ LANGUAGE 'plpythonu' VOLATILE SECURITY DEFINER;
 
 CREATE OR REPLACE
-FUNCTION cartodb._CDB_Group_RemoveUsers_API(group_name text, usernames text)
+FUNCTION cartodb._CDB_Group_RemoveUsers_API(group_name text, usernames text[])
     RETURNS VOID AS
 $$
     import string
     import urllib
 
     url = '/api/v1/databases/{0}/groups/%s/users' % (urllib.pathname2url(group_name))
-    body = "{ \"users\": [\"%s\"] }" % "\",\"".join(usernames.split(','))
+    body = "{ \"users\": [\"%s\"] }" % "\",\"".join(usernames)
     query = "select cartodb._CDB_Group_API_Request('DELETE', '%s', '%s', '{200, 404}') as response_status" % (url, body)
     plpy.execute(query)
 $$ LANGUAGE 'plpythonu' VOLATILE SECURITY DEFINER;