diff --git a/Library/Homebrew/brew.rb b/Library/Homebrew/brew.rb
index 8c5386612c..2cc339a834 100644
--- a/Library/Homebrew/brew.rb
+++ b/Library/Homebrew/brew.rb
@@ -78,7 +78,8 @@ begin
   # - a help flag is passed AND a command is matched
   # - a help flag is passed AND there is no command specified
   # - no arguments are passed
-  if empty_argv || help_flag
+  # - if cmd is Cask, let Cask handle the help command instead
+  if (empty_argv || help_flag) && cmd != "cask"
     require "cmd/help"
     Homebrew.help cmd, empty_argv: empty_argv
     # `Homebrew.help` never returns, except for external/unknown commands.
@@ -116,8 +117,11 @@ begin
     if Process.uid.zero? && !brew_uid.zero?
       tap_commands += %W[/usr/bin/sudo -u ##{brew_uid}]
     end
+    # Unset HOMEBREW_HELP to avoid confusing the tap
+    ENV.delete("HOMEBREW_HELP") if help_flag
     tap_commands += %W[#{HOMEBREW_BREW_FILE} tap #{possible_tap}]
     safe_system(*tap_commands)
+    ENV["HOMEBREW_HELP"] = "1" if help_flag
     exec HOMEBREW_BREW_FILE, cmd, *ARGV
   end
 rescue UsageError => e
diff --git a/Library/Homebrew/cask/lib/hbc/cli.rb b/Library/Homebrew/cask/lib/hbc/cli.rb
index 9283802d5e..e147c82809 100644
--- a/Library/Homebrew/cask/lib/hbc/cli.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli.rb
@@ -154,7 +154,7 @@ module Hbc
     def run
       command_name, *args = detect_command_and_arguments(*@args)
       command = if help?
-        args.unshift(command_name)
+        args.unshift(command_name) unless command_name.nil?
         "help"
       else
         self.class.lookup_command(command_name)
@@ -230,8 +230,7 @@ module Hbc
 
         return if @command == "help" && @args.empty?
 
-        unknown_command = @args.empty? ? @command : @args.first
-        raise ArgumentError, "Unknown command: #{unknown_command}"
+        raise ArgumentError, "help does not take arguments."
       end
 
       def purpose