diff --git a/resources/functionMap.php b/resources/functionMap.php
index 1123f5910e..d5b4e6a7ea 100644
--- a/resources/functionMap.php
+++ b/resources/functionMap.php
@@ -8016,7 +8016,7 @@
 'nsapi_response_headers' => ['array'],
 'nsapi_virtual' => ['bool', 'uri'=>'string'],
 'nthmac' => ['string', 'clent'=>'string', 'data'=>'string'],
-'number_format' => ['string', 'number'=>'float', 'num_decimal_places='=>'int', 'dec_separator='=>'string|null', 'thousands_separator='=>'string|null'],
+'number_format' => ['non-empty-string', 'number'=>'float', 'num_decimal_places='=>'int', 'dec_separator='=>'string|null', 'thousands_separator='=>'string|null'],
 'NumberFormatter::__construct' => ['void', 'locale'=>'string', 'style'=>'int', 'pattern='=>'string'],
 'NumberFormatter::create' => ['NumberFormatter', 'locale'=>'string', 'style'=>'int', 'pattern='=>'string'],
 'NumberFormatter::format' => ['string|false', 'num'=>'', 'type='=>'int'],