diff --git a/spec/bundled_gems.mspec b/spec/bundled_gems.mspec
index f17f32f1b2..48f917c809 100644
--- a/spec/bundled_gems.mspec
+++ b/spec/bundled_gems.mspec
@@ -2,7 +2,7 @@ load File.dirname(__FILE__) + '/default.mspec'
 
 class MSpecScript
   test_bundled_gems = get(:stdlibs).to_a & get(:bundled_gems).to_a
-  unless ENV["BUNDLED_GEMS"].nil?
+  unless ENV["BUNDLED_GEMS"].nil? || ENV["BUNDLED_GEMS"].empty?
     test_bundled_gems = ENV["BUNDLED_GEMS"].split(",").map do |gem|
       test_bundled_gems.find{|test_gem| test_gem.include?(gem) }
     end.compact
diff --git a/tool/test-bundled-gems.rb b/tool/test-bundled-gems.rb
index 9aad4c3b63..8ea365112c 100644
--- a/tool/test-bundled-gems.rb
+++ b/tool/test-bundled-gems.rb
@@ -24,7 +24,7 @@ failed = []
 File.foreach("#{gem_dir}/bundled_gems") do |line|
   next if /^\s*(?:#|$)/ =~ line
   gem = line.split.first
-  next unless bundled_gems.delete_prefix("BUNDLED_GEMS=").split(",").include?(gem)
+  next unless bundled_gems.empty? || bundled_gems.split(",").include?(gem)
   next unless File.directory?("#{gem_dir}/src/#{gem}/test")
 
   test_command = "#{ruby} -C #{gem_dir}/src/#{gem} #{rake} test"