diff --git a/tools/line_length.py b/tools/line_length.py
index 2c9161a7daf0..dd816384ade0 100755
--- a/tools/line_length.py
+++ b/tools/line_length.py
@@ -33,7 +33,7 @@ def get_git_added_lines() -> LineGenerator:
     current_file = None
     current_lineno = None
     lines_left = 0
-    for line in str(proc.stdout).splitlines():
+    for line in proc.stdout.decode(errors="replace").splitlines():
         match_file = re.match(r"^\+\+\+ b/(.*)$", line)
         if match_file:
             current_file = match_file.group(1)