diff --git a/library/Zend/Locale/Format.php b/library/Zend/Locale/Format.php
index c937b92cf5..8a5c8d5232 100644
--- a/library/Zend/Locale/Format.php
+++ b/library/Zend/Locale/Format.php
@@ -516,6 +516,10 @@ public static function isNumber($input, array $options = [])
         if (!self::_getUniCodeSupport()) {
             trigger_error("Sorry, your PCRE extension does not support UTF8 which is needed for the I18N core", E_USER_NOTICE);
         }
+        
+        if($input === null ) {
+            return FALSE;
+        }
 
         $options = self::_checkOptions($options) + self::$_options;
 
@@ -524,7 +528,10 @@ public static function isNumber($input, array $options = [])
 
         $regexs = Zend_Locale_Format::_getRegexForType('decimalnumber', $options);
         $regexs = array_merge($regexs, Zend_Locale_Format::_getRegexForType('scientificnumber', $options));
-        if (!empty($input) && ($input[0] == $symbols['decimal'])) {
+        
+        $firstChar = substr($input,0,1);
+        
+        if (!empty($input) && ($firstChar == $symbols['decimal'])) {
             $input = 0 . $input;
         }
         foreach ($regexs as $regex) {