don't use #tap so 1.8.x works

.gitignore

@@ -3,4 +3,4 @@ tmp
 pkg
 .swo
 *~
-
+*.gem

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    appraisal (0.3.4)
+    appraisal (0.3.5)
       aruba (~> 0.3.6)
       bundler
       rake

lib/appraisal/file.rb

@@ -22,9 +22,9 @@ def each(&block)
     end
 
     def appraise(name, &block)
-      @appraisals << Appraisal.new(name, gemfile).tap do |appraisal|
-        appraisal.instance_eval(&block)
-      end
+      appraisal = Appraisal.new(name, gemfile)
+      appraisal.instance_eval(&block)
+      @appraisals << appraisal
     end
 
     private

lib/appraisal/gemfile.rb

@@ -31,13 +31,13 @@ def to_s
     end
 
     def dup
-      Gemfile.new.tap do |gemfile|
-        gemfile.source @source
-        dependencies.values.each do |dependency|
-          gemfile.gem(dependency.name, *dependency.requirements)
-        end
-        gemfile.gemspec(@gemspec.options) if @gemspec
+      gemfile = Gemfile.new
+      gemfile.source @source
+      dependencies.values.each do |dependency|
+        gemfile.gem(dependency.name, *dependency.requirements)
       end
+      gemfile.gemspec(@gemspec.options) if @gemspec
+      gemfile
     end
 
     def gemspec(options = {})