1 files changed, 17 insertions, 3 deletions
diff --git a/Library/Homebrew/dependencies.rb b/Library/Homebrew/dependencies.rb
index 5d5b5ab0d..7c2ff7d1b 100644
--- a/Library/Homebrew/dependencies.rb
+++ b/Library/Homebrew/dependencies.rb
@@ -21,7 +21,7 @@ class DependencyCollector
 
   def initialize
     @deps = Dependencies.new
-    @requirements = Set.new
+    @requirements = ComparableSet.new
   end
 
   def add spec
@@ -196,6 +196,9 @@ end
 # This requirement is used to require an X11 implementation,
 # optionally with a minimum version number.
 class X11Dependency < Requirement
+  include Comparable
+  attr_reader :min_version
+
   def initialize min_version=nil
     @min_version = min_version
   end
@@ -217,9 +220,20 @@ class X11Dependency < Requirement
     ENV.x11
   end
 
-  def hash
-    "X11".hash
+  def <=> other
+    unless other.is_a? X11Dependency
+      raise TypeError, "expected X11Dependency"
+    end
+
+    if other.min_version.nil?
+      1
+    elsif @min_version.nil?
+      -1
+    else
+      @min_version <=> other.min_version
+    end
   end
+
 end