diff --git a/application/applicationextension.inc.php b/application/applicationextension.inc.php
index e748b60a1..2bc81dfe8 100644
--- a/application/applicationextension.inc.php
+++ b/application/applicationextension.inc.php
@@ -581,6 +581,14 @@ class RestResult
 	 * Result: the input structure is not a valid JSON string
 	 */
 	const INVALID_JSON = 4;
+	/**
+	 * Result: the parameter 'auth_user' is missing, authentication aborted
+	 */
+	const MISSING_AUTH_USER = 5;
+	/**
+	 * Result: the parameter 'auth_pwd' is missing, authentication aborted
+	 */
+	const MISSING_AUTH_PWD = 6;
 	/**
 	 * Result: no operation is available for the specified version
 	 */
diff --git a/webservices/rest.php b/webservices/rest.php
index cf943b195..fbe30e696 100644
--- a/webservices/rest.php
+++ b/webservices/rest.php
@@ -96,7 +96,15 @@ try
 	utils::UseParamFile();
 
 	$sAuthUser = utils::ReadParam('auth_user', null, false, 'raw_data');
+	if ($sAuthUser === null)
+	{
+		throw new Exception("Missing parameter 'auth_user'", RestResult::MISSING_AUTH_USER);
+	}
 	$sAuthPwd = utils::ReadParam('auth_pwd', null, false, 'raw_data');
+	if ($sAuthPwd === null)
+	{
+		throw new Exception("Missing parameter 'auth_pwd'", RestResult::MISSING_AUTH_PWD);
+	}
 	if (UserRights::CheckCredentials($sAuthUser, $sAuthPwd))
 	{
 		UserRights::Login($sAuthUser); // Login & set the user's language