diff --git a/esphome/config_validation.py b/esphome/config_validation.py
index 2746f574ba..ebfedf2017 100644
--- a/esphome/config_validation.py
+++ b/esphome/config_validation.py
@@ -1200,7 +1200,7 @@ def hostname(value):
     Maximum length is 63 characters per RFC 1035.
 
     Note: If this limit is changed, update MAX_NAME_WITH_SUFFIX_SIZE in
-    esphome/core/application.h to accommodate the new maximum length.
+    esphome/core/helpers.cpp to accommodate the new maximum length.
     """
     value = string(value)
     if re.match(r"^[a-z0-9-]{1,63}$", value, re.IGNORECASE) is not None: