diff --git a/outputjson.php b/outputjson.php
index 6b629f7..48871f7 100644
--- a/outputjson.php
+++ b/outputjson.php
@@ -4,7 +4,9 @@
     @author Dominique Fournier <dominique@fournier38.fr> */
 
 require_once ("output.php");
-/** Display in JSOn the data provided */
+/** Display in JSON the data provided 
+  * The data must NOT be binary !
+  */
 class outputjson extends output
 {
   /** Don't allow to output in JSON if the functions are not available in PHP */
@@ -25,7 +27,11 @@ class outputjson extends output
     @header('Cache-Control: post-check=0, pre-check=0', false);
     @header('Pragma: no-cache');
     @header ("Content-Type: application/json");
-    echo json_encode ($data);
+    $content = json_encode ($data);
+    if (json_last_error () !== 0)
+      printf (dgettext("domframework", "Can't send in JSON invalid data : %s"),
+                       json_last_error_msg ());
+    echo $content;
     if (!defined ("PHPUNIT"))
       exit;
   }