diff --git a/htdocs/core/lib/json.lib.php b/htdocs/core/lib/json.lib.php
index b5a53c7f888..15f54b75f97 100644
--- a/htdocs/core/lib/json.lib.php
+++ b/htdocs/core/lib/json.lib.php
@@ -267,7 +267,7 @@ function dol_json_decode($json, $assoc = false)
 		} else {
 			$out .= $json[$i];
 		}
-		if ($i > 0 && $json[$i] == '"' && $json[($i - 1)] != "\\") {
+		if ($i >= 1 && $json[$i] == '"' && $json[$i - 1] != "\\") {
 			$comment = !$comment;
 		}
 	}