diff --git a/Library/Homebrew/cmd/install.rb b/Library/Homebrew/cmd/install.rb
index 468eb3d375..4e1705c74b 100644
--- a/Library/Homebrew/cmd/install.rb
+++ b/Library/Homebrew/cmd/install.rb
@@ -19,6 +19,10 @@ 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 7b0a11311e..c2e1a9c2e7 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?