1 files changed, 11 insertions, 1 deletions
diff --git a/Library/Homebrew/dependencies.rb b/Library/Homebrew/dependencies.rb
index 6a4c3e228..43596ad6c 100644
--- a/Library/Homebrew/dependencies.rb
+++ b/Library/Homebrew/dependencies.rb
@@ -1,3 +1,5 @@
+require 'set'
+
 ## This file defines dependencies and requirements.
 ##
 ## A dependency is a formula that another formula needs to install.
@@ -21,7 +23,7 @@ class DependencyCollector
 
   def initialize
     @deps = Dependencies.new
-    @external_deps = []
+    @external_deps = Set.new
   end
 
   def add spec
@@ -119,6 +121,14 @@ class Requirement
   def fatal?; false; end
   def message; ""; end
   def modify_build_environment; nil end
+
+  def eql?(other)
+    other.is_a? self.class and hash == other.hash
+  end
+
+  def hash
+    @message.hash
+  end
 end