diff --git a/esphome/build_helpers/size_summary.py b/esphome/build_helpers/size_summary.py
index 8014b9e527..5068e76d2d 100644
--- a/esphome/build_helpers/size_summary.py
+++ b/esphome/build_helpers/size_summary.py
@@ -4,7 +4,11 @@ from __future__ import annotations
 
 
 def format_bar(used: int, total: int) -> str:
-    """Match PlatformIO's ``_format_availale_bytes`` (pioupload.py) exactly."""
+    """Match PlatformIO's ``_format_availale_bytes`` (pioupload.py) exactly.
+
+    The upstream helper's name really is spelled that way; keep the citation
+    verbatim so it stays greppable in the PlatformIO source.
+    """
     pct_raw = used / total if total else 0
     blocks = 10
     filled = min(int(round(blocks * pct_raw)), blocks)