diff --git a/Library/Homebrew/formula_versions.rb b/Library/Homebrew/formula_versions.rb
index 07770b41c6..fc3c1cbaa8 100644
--- a/Library/Homebrew/formula_versions.rb
+++ b/Library/Homebrew/formula_versions.rb
@@ -54,7 +54,7 @@ class FormulaVersions
     formula_at_revision(rev) { |f| f.version }
   end
 
-  def formula_at_revision rev, &block
+  def formula_at_revision(rev)
     FileUtils.mktemp(f.name) do
       path = Pathname.pwd.join("#{f.name}.rb")
       path.write file_contents_at_revision(rev)