diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index b488e4ed8e..524d85b8d5 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,3 +1,7 @@
+*  The `log:clear` task clear all environments log files by default.
+
+    *Yuji Yaginuma*
+
 *   Allow the use of listen's 3.1.x branch
 
     *Esteban Santana Santana*
diff --git a/railties/lib/rails/tasks/log.rake b/railties/lib/rails/tasks/log.rake
index c376234fee..ba796845d7 100644
--- a/railties/lib/rails/tasks/log.rake
+++ b/railties/lib/rails/tasks/log.rake
@@ -3,7 +3,7 @@ namespace :log do
   ##
   # Truncates all/specified log files
   # ENV['LOGS']
-  #   - defaults to standard environment log files i.e. 'development,test,production'
+  #   - defaults to all environments log files i.e. 'development,test,production'
   #   - ENV['LOGS']=all truncates all files i.e. log/*.log
   #   - ENV['LOGS']='test,development' truncates only specified files
   desc "Truncates all/specified *.log files in log/ to zero bytes (specify which logs with LOGS=test,development)"
@@ -19,7 +19,7 @@ namespace :log do
     elsif ENV["LOGS"]
       log_files_to_truncate(ENV["LOGS"])
     else
-      log_files_to_truncate("development,test,production")
+      log_files_to_truncate(all_environments.join(","))
     end
   end
 
@@ -33,4 +33,8 @@ namespace :log do
     f = File.open(file, "w")
     f.close
   end
+
+  def all_environments
+    Dir["config/environments/*.rb"].map { |fname| File.basename(fname, ".*") }
+  end
 end
diff --git a/railties/test/application/rake/log_test.rb b/railties/test/application/rake/log_test.rb
new file mode 100644
index 0000000000..fdd3c71fe8
--- /dev/null
+++ b/railties/test/application/rake/log_test.rb
@@ -0,0 +1,33 @@
+require "isolation/abstract_unit"
+
+module ApplicationTests
+  module RakeTests
+    class LogTest < ActiveSupport::TestCase
+      include ActiveSupport::Testing::Isolation
+
+      def setup
+        build_app
+      end
+
+      def teardown
+        teardown_app
+      end
+
+      test "log:clear clear all environments log files by default" do
+        Dir.chdir(app_path) do
+          File.open("config/environments/staging.rb", "w")
+
+          File.write("log/staging.log", "staging")
+          File.write("log/test.log", "test")
+          File.write("log/dummy.log", "dummy")
+
+          `rails log:clear`
+
+          assert_equal 0, File.size("log/test.log")
+          assert_equal 0, File.size("log/staging.log")
+          assert_equal 5, File.size("log/dummy.log")
+        end
+      end
+    end
+  end
+end