diff --git a/Library/Homebrew/requirements/x11_dependency.rb b/Library/Homebrew/requirements/x11_dependency.rb
index 35e9be723e..4b030445cc 100644
--- a/Library/Homebrew/requirements/x11_dependency.rb
+++ b/Library/Homebrew/requirements/x11_dependency.rb
@@ -33,10 +33,10 @@ class X11Dependency < Requirement
       0
     elsif other.min_version.nil?
       1
-    elsif @min_version.nil?
+    elsif min_version.nil?
       -1
     else
-      @min_version <=> other.min_version
+      min_version <=> other.min_version
     end
   end