diff --git a/parsecsv.lib.php b/parsecsv.lib.php
index 54c5295..416bb61 100644
--- a/parsecsv.lib.php
+++ b/parsecsv.lib.php
@@ -494,11 +494,11 @@ class parseCSV {
      */
     public function encoding ($input = null, $output = null) {
         $this->convert_encoding = true;
-        if ( $input !== null ) {
+        if (!is_null($input)) {
             $this->input_encoding = $input;
         }
 
-        if ( $output !== null )  {
+        if (!is_null($output)) {
             $this->output_encoding = $output;
         }
     }