diff --git a/tools/functional/generator.py b/tools/functional/generator.py
index 545ba672bd5..bba6879ba04 100644
--- a/tools/functional/generator.py
+++ b/tools/functional/generator.py
@@ -392,7 +392,7 @@ def __init__(self, fmt):
         self._max_keyword_args_count = count
 
     @property
-    def num_of_args():
+    def num_of_args(self):
         return len(self._args)
 
     def to_string(self, to_cpp=False, drop_name=False):