diff --git a/nav2_common/nav2_common/launch/rewritten_yaml.py b/nav2_common/nav2_common/launch/rewritten_yaml.py
index 0c1cfb51bb4eeb5d81ce7dde2d3125df3bc72727..d109794ef07e30683afaefb24cf699369c65dd0f 100644
--- a/nav2_common/nav2_common/launch/rewritten_yaml.py
+++ b/nav2_common/nav2_common/launch/rewritten_yaml.py
@@ -59,6 +59,7 @@ class RewrittenYaml(launch.Substitution):
     self.__param_rewrites = {}
     self.__key_rewrites = {}
     self.__convert_types = convert_types
+    self.__root_key = None
     for key in param_rewrites:
         self.__param_rewrites[key] = normalize_to_list_of_substitutions(param_rewrites[key])
     if key_rewrites is not None: