diff --git a/Library/Homebrew/cmd/install.rb b/Library/Homebrew/cmd/install.rb
index 4e1705c74b..468eb3d375 100644
--- a/Library/Homebrew/cmd/install.rb
+++ b/Library/Homebrew/cmd/install.rb
@@ -19,10 +19,6 @@ module Homebrew extend self
       end
     end
 
-    if ARGV.include? '--head'
-      raise "Specify `--HEAD` in uppercase to build from trunk."
-    end
-
     ARGV.named.each do |name|
       # if a formula has been tapped ignore the blacklisting
       if not File.file? HOMEBREW_REPOSITORY/"Library/Formula/#{name}.rb"
diff --git a/Library/Homebrew/extend/ARGV.rb b/Library/Homebrew/extend/ARGV.rb
index c2e1a9c2e7..7b0a11311e 100644
--- a/Library/Homebrew/extend/ARGV.rb
+++ b/Library/Homebrew/extend/ARGV.rb
@@ -111,7 +111,7 @@ module HomebrewArgvExtension
   end
 
   def build_head?
-    include? '--HEAD'
+    include?('--HEAD') || include?('--head')
   end
 
   def build_devel?