diff --git a/fluentd.gemspec b/fluentd.gemspec
index cd942d72c1..6da1c471ce 100644
--- a/fluentd.gemspec
+++ b/fluentd.gemspec
@@ -39,13 +39,13 @@ Gem::Specification.new do |gem|
     gem.add_runtime_dependency("certstore_c", ["~> 0.1.2"])
   end
 
-  gem.add_development_dependency("rake", ["~> 12.0"])
+  gem.add_development_dependency("rake", ["~> 13.0"])
   gem.add_development_dependency("flexmock", ["~> 2.0"])
   gem.add_development_dependency("parallel_tests", ["~> 0.15.3"])
   gem.add_development_dependency("simplecov", ["~> 0.7"])
   gem.add_development_dependency("rr", ["~> 1.0"])
-  gem.add_development_dependency("timecop", ["~> 0.3"])
-  gem.add_development_dependency("test-unit", ["~> 3.2"])
+  gem.add_development_dependency("timecop", ["~> 0.9"])
+  gem.add_development_dependency("test-unit", ["~> 3.3"])
   gem.add_development_dependency("test-unit-rr", ["~> 1.0"])
   gem.add_development_dependency("oj", [">= 2.14", "< 4"])
 end
diff --git a/lib/fluent/command/plugin_generator.rb b/lib/fluent/command/plugin_generator.rb
index e020c8998e..dc11eb92d9 100644
--- a/lib/fluent/command/plugin_generator.rb
+++ b/lib/fluent/command/plugin_generator.rb
@@ -281,7 +281,8 @@ def initialize
       @text = ""
       @preamble_source = ""
       @preamble = nil
-      URI.open(LICENSE_URL) do |io|
+      uri = URI.parse(LICENSE_URL)
+      uri.open do |io|
         @text = io.read
       end
       @preamble_source = @text[/^(\s*Copyright.+)/m, 1]