diff --git a/benchmark/bm_so_lists.rb b/benchmark/bm_so_lists.rb
index f620297f4..3b9f291b8 100644
--- a/benchmark/bm_so_lists.rb
+++ b/benchmark/bm_so_lists.rb
@@ -5,7 +5,7 @@
 NUM = 300
 SIZE = 10000
 
-def test_lists()
+def test_lists
   # create a list of integers (Li1) from 1 to SIZE
   li1 = (1..SIZE).to_a
   # copy the list to li2 (not by individual items)
diff --git a/lib/mruby/build/load_gems.rb b/lib/mruby/build/load_gems.rb
index 4142881ab..34d35ebdd 100644
--- a/lib/mruby/build/load_gems.rb
+++ b/lib/mruby/build/load_gems.rb
@@ -75,7 +75,7 @@ module MRuby
       def git?()        return !!@repo;                     end
       def gemname()     return File.basename(@gemdir);      end
 
-      def hash()
+      def hash
         return [@gemdir, @repo, @branch, @commit, @canonical, @path].hash
       end
 
diff --git a/test/t/bs_block.rb b/test/t/bs_block.rb
index f4e4da375..c37d1b538 100644
--- a/test/t/bs_block.rb
+++ b/test/t/bs_block.rb
@@ -374,7 +374,7 @@ assert('BS Block [ruby-dev:31147]') do
 end
 
 assert('BS Block [ruby-dev:31160]') do
-  def m()
+  def m
     yield
   end
   assert_nil m {|(v,(*))|}
@@ -389,7 +389,7 @@ assert('BS Block [issue #750]') do
 end
 
 assert('BS Block 31') do
-  def m()
+  def m
     yield
   end
   assert_nil m {|((*))|}
diff --git a/test/t/module.rb b/test/t/module.rb
index 8179ac78d..c18276a9f 100644
--- a/test/t/module.rb
+++ b/test/t/module.rb
@@ -729,14 +729,14 @@ end
 
 assert('Issue 1467') do
   module M1
-    def initialize()
+    def initialize
       super()
     end
   end
 
   class C1
     include M1
-      def initialize()
+      def initialize
         super()
       end
   end