diff --git a/Library/Homebrew/utils/gzip.rb b/Library/Homebrew/utils/gzip.rb
index 4bac85685d..acb70088ec 100644
--- a/Library/Homebrew/utils/gzip.rb
+++ b/Library/Homebrew/utils/gzip.rb
@@ -1,9 +1,9 @@
-# typed: true
+# typed: strict
 # frozen_string_literal: true
 
 # Apple's gzip also uses zlib so use the same buffer size here.
 # https://github.com/apple-oss-distributions/file_cmds/blob/file_cmds-400/gzip/gzip.c#L147
-GZIP_BUFFER_SIZE = 64 * 1024
+GZIP_BUFFER_SIZE = T.let(64 * 1024, Integer)
 
 module Utils
   # Helper functions for creating gzip files.