diff --git a/Library/Homebrew/brew.rb b/Library/Homebrew/brew.rb
index e62c81c632..fd877a3610 100644
--- a/Library/Homebrew/brew.rb
+++ b/Library/Homebrew/brew.rb
@@ -136,9 +136,9 @@ begin
   end
 rescue UsageError => e
   require "help"
-  Homebrew::Help.help cmd, remaining_args: T.must(args).remaining, usage_error: e.message
+  Homebrew::Help.help cmd, remaining_args: args&.remaining, usage_error: e.message
 rescue SystemExit => e
-  onoe "Kernel.exit" if T.must(args).debug? && !e.success?
+  onoe "Kernel.exit" if args&.debug? && !e.success?
   $stderr.puts Utils::Backtrace.clean(e) if args&.debug? || ARGV.include?("--debug")
   raise
 rescue Interrupt
diff --git a/Library/Homebrew/cli/parser.rb b/Library/Homebrew/cli/parser.rb
index df4119a001..9ad7e52eb0 100644
--- a/Library/Homebrew/cli/parser.rb
+++ b/Library/Homebrew/cli/parser.rb
@@ -250,7 +250,7 @@ module Homebrew
       end
 
       sig {
-        params(names: String, description: T.nilable(String), replacement: T.untyped, depends_on: T.nilable(String),
+        params(names: String, description: T.nilable(String), replacement: T.any(Symbol, String, NilClass), depends_on: T.nilable(String),
                hidden: T::Boolean).void
       }
       def flag(*names, description: nil, replacement: nil, depends_on: nil, hidden: false)