diff --git a/plugin.php b/plugin.php
index fb7f1e9..3b54f8e 100644
--- a/plugin.php
+++ b/plugin.php
@@ -280,7 +280,7 @@ function ldapauth_merge_users() {
 	if ( !ldapauth_environment_check() ) {
 		die( 'Invalid configuration for YOURLS LDAP plugin. Check PHP error log.' );
 	}
-	if(LDAPAUTH_USERCACHE_TYPE==1 && isset(yourls_get_option('ldapauth_usercache'))) {
+	if(LDAPAUTH_USERCACHE_TYPE==1 && null !== yourls_get_option('ldapauth_usercache')) {
 		ldapauth_debug("Merging text file users and cached LDAP users");
 		$yourls_user_passwords = array_merge($yourls_user_passwords, yourls_get_option('ldapauth_usercache'));
 	}