diff --git a/telethon_generator/tl_generator.py b/telethon_generator/tl_generator.py
index fde3cd22..5ee12969 100644
--- a/telethon_generator/tl_generator.py
+++ b/telethon_generator/tl_generator.py
@@ -314,11 +314,11 @@ class TLGenerator:
 
         for ra in repeated_args.values():
             if len(ra) > 1:
-                cnd1 = ('self.{} is None'.format(a.name) for a in ra)
-                cnd2 = ('self.{} is not None'.format(a.name) for a in ra)
+                cnd1 = ('self.{}'.format(a.name) for a in ra)
+                cnd2 = ('not self.{}'.format(a.name) for a in ra)
                 builder.writeln(
                     "assert ({}) or ({}), '{} parameters must all "
-                    "be None or neither be None'".format(
+                    "be False-y (like None) or all me True-y''".format(
                         ' and '.join(cnd1), ' and '.join(cnd2),
                         ', '.join(a.name for a in ra)
                     )