diff --git a/Library/Homebrew/formula_pin.rb b/Library/Homebrew/formula_pin.rb
index 842d108c2c..9a9aa4cedf 100644
--- a/Library/Homebrew/formula_pin.rb
+++ b/Library/Homebrew/formula_pin.rb
@@ -18,7 +18,7 @@ class FormulaPin
   end
 
   def pin
-    pin_at(@f.rack.subdirs.map { |d| Keg.new(d).version }.first)
+    pin_at(@f.rack.subdirs.map { |d| Keg.new(d).version }.max)
   end
 
   def unpin