diff --git a/htdocs/core/lib/security.lib.php b/htdocs/core/lib/security.lib.php
index d1d0d7ed7d0..5a610090be2 100644
--- a/htdocs/core/lib/security.lib.php
+++ b/htdocs/core/lib/security.lib.php
@@ -257,7 +257,7 @@ function dol_verifyHash($chain, $hash, $type = '0')
 	global $conf;
 
 	if ($type == '0' && !empty($conf->global->MAIN_SECURITY_HASH_ALGO) && $conf->global->MAIN_SECURITY_HASH_ALGO == 'password_hash' && function_exists('password_verify')) {
-		if ($hash[0] == '$') {
+		if (! empty($hash[0]) && $hash[0] == '$') {
 			return password_verify($chain, $hash);
 		} elseif (strlen($hash) == 32) {
 			return dol_verifyHash($chain, $hash, '3'); // md5