diff --git a/mrbgems/mruby-pack/test/pack.rb b/mrbgems/mruby-pack/test/pack.rb
index 16db6607b..4dd7f4a90 100644
--- a/mrbgems/mruby-pack/test/pack.rb
+++ b/mrbgems/mruby-pack/test/pack.rb
@@ -1,4 +1,3 @@
-# coding: utf-8
 PACK_IS_LITTLE_ENDIAN = "\x01\00".unpack('S')[0] == 0x01
 
 def assert_pack tmpl, packed, unpacked
diff --git a/mrbgems/mruby-string-ext/test/numeric.rb b/mrbgems/mruby-string-ext/test/numeric.rb
index dfcb9ebf4..f79235de0 100644
--- a/mrbgems/mruby-string-ext/test/numeric.rb
+++ b/mrbgems/mruby-string-ext/test/numeric.rb
@@ -1,5 +1,3 @@
-# coding: utf-8
-
 assert('Integer#chr') do
   assert_equal("A", 65.chr)
   assert_equal("B", 0x42.chr)
diff --git a/mrbgems/mruby-string-ext/test/string.rb b/mrbgems/mruby-string-ext/test/string.rb
index 7be673aa6..eb731c503 100644
--- a/mrbgems/mruby-string-ext/test/string.rb
+++ b/mrbgems/mruby-string-ext/test/string.rb
@@ -1,4 +1,3 @@
-# coding: utf-8
 ##
 # String(Ext) Test
 
diff --git a/mrbgems/mruby-symbol-ext/test/symbol.rb b/mrbgems/mruby-symbol-ext/test/symbol.rb
index a4fb27733..239f8c270 100644
--- a/mrbgems/mruby-symbol-ext/test/symbol.rb
+++ b/mrbgems/mruby-symbol-ext/test/symbol.rb
@@ -1,4 +1,3 @@
-# coding: utf-8
 ##
 # Symbol(Ext) Test
 
diff --git a/mrblib/array.rb b/mrblib/array.rb
index 657a7a5e4..4646951f7 100644
--- a/mrblib/array.rb
+++ b/mrblib/array.rb
@@ -1,4 +1,3 @@
-# coding: utf-8
 ##
 # Array
 #
diff --git a/mruby-source.gemspec b/mruby-source.gemspec
index 9717ad5f2..6dff87e87 100644
--- a/mruby-source.gemspec
+++ b/mruby-source.gemspec
@@ -1,4 +1,3 @@
-# coding: utf-8
 lib = File.expand_path('../lib', __FILE__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'mruby/source'
diff --git a/test/t/string.rb b/test/t/string.rb
index 2e9025c97..11b5cae0f 100644
--- a/test/t/string.rb
+++ b/test/t/string.rb
@@ -1,4 +1,3 @@
-# coding: utf-8
 ##
 # String ISO Test