diff --git a/oauth/LDAP/LDAP.php b/oauth/LDAP/LDAP.php
index d9f79b8..42ed2fc 100755
--- a/oauth/LDAP/LDAP.php
+++ b/oauth/LDAP/LDAP.php
@@ -134,7 +134,7 @@ class LDAP implements LDAPInterface
         $data = ldap_first_entry($this->ldap_server, $result);
         if (!$data)
         {
-            throw new Exception('An error has occured during ldap_first_entry execution. Please check parameter of LDAP/checkLogin.');
+            throw new Exception('No result from LDAP server', 404);
         }
         $dn = ldap_get_dn($this->ldap_server, $data);
         if (!$dn)
diff --git a/oauth/resource.php b/oauth/resource.php
index b083bb8..bd131d8 100755
--- a/oauth/resource.php
+++ b/oauth/resource.php
@@ -86,7 +86,17 @@ try
 }
 catch (Exception $e)
 {
-	$resp = array("error" => "Impossible to get data", "message" => $e->getMessage());
+    if ($e->getCode() == 404) {
+	$resp = [
+	    "error" => "User not found",
+	    "message" => "<b>$user</b> is not in the group of authorized users."
+	];
+    } else {
+	$resp = array(
+	    "error" => "Impossible to get data",
+	    "message" => $e->getMessage()
+	);
+    }
 }
 
 // send data or error message in JSON format