diff --git a/change_level.py b/change_level.py
index 35feb556..e9213548 100755
--- a/change_level.py
+++ b/change_level.py
@@ -22,6 +22,14 @@ if __name__ == '__main__':
         print "Error: app '%s' is not present in %s" % (app_id, app_list_name)
         sys.exit(1)
 
-    app_list[app_id]["level"] = level
+    if not level.isdigit():
+        print "Error: app level must be a number, it's '%s'" % level
+        sys.exit(1)
+
+    if not 0 <= int(level) <= 10:
+        print "Error: app level must be between 0 and 10, it's '%s'" % level
+        sys.exit(1)
+
+    app_list[app_id]["level"] = int(level)
 
     open(app_list_name, "w").write("\n".join(json.dumps(app_list, indent=4, sort_keys=True).split(" \n")) + "\n")