diff --git a/lib/drb/acl.rb b/lib/drb/acl.rb
index 8d06b25..72e034e 100644
--- a/lib/drb/acl.rb
+++ b/lib/drb/acl.rb
@@ -223,7 +223,7 @@ class ACL
       when 'deny'
         @deny.add(domain)
       else
-        raise "Invalid ACL entry #{list.to_s}"
+        raise "Invalid ACL entry #{list}"
       end
       i += 2
     end
diff --git a/lib/erb.rb b/lib/erb.rb
index b30812f..c372f56 100644
--- a/lib/erb.rb
+++ b/lib/erb.rb
@@ -548,7 +548,7 @@ class ERB
       def initialize(compiler, enc=nil)
         @compiler = compiler
         @line = []
-        @script = enc ? "#coding:#{enc.to_s}\n" : ""
+        @script = enc ? "#coding:#{enc}\n" : ""
         @compiler.pre_cmd.each do |x|
           push(x)
         end
diff --git a/lib/observer.rb b/lib/observer.rb
index 99610f7..10f2eb0 100644
--- a/lib/observer.rb
+++ b/lib/observer.rb
@@ -127,7 +127,7 @@ module Observable
   def add_observer(observer, func=:update)
     @observer_peers = {} unless defined? @observer_peers
     unless observer.respond_to? func
-      raise NoMethodError, "observer does not respond to `#{func.to_s}'"
+      raise NoMethodError, "observer does not respond to `#{func}'"
     end
     @observer_peers[observer] = func
   end
diff --git a/lib/rake/invocation_chain.rb b/lib/rake/invocation_chain.rb
index 6904351..25ad766 100644
--- a/lib/rake/invocation_chain.rb
+++ b/lib/rake/invocation_chain.rb
@@ -31,7 +31,7 @@ module Rake
     private

     def prefix
-      "#{tail.to_s} => "
+      "#{tail} => "
     end

     # Null object for an empty chain.
diff --git a/lib/rubygems/command_manager.rb b/lib/rubygems/command_manager.rb
index fdee064..54636bf 100644
--- a/lib/rubygems/command_manager.rb
+++ b/lib/rubygems/command_manager.rb
@@ -136,7 +136,7 @@ class Gem::CommandManager
   def run(args, build_args=nil)
     process_args(args, build_args)
   rescue StandardError, Timeout::Error => ex
-    alert_error "While executing gem ... (#{ex.class})\n    #{ex.to_s}"
+    alert_error "While executing gem ... (#{ex.class})\n    #{ex}"
     ui.backtrace ex

     terminate_interaction(1)
diff --git a/lib/rubygems/config_file.rb b/lib/rubygems/config_file.rb
index cf14017..1f4afba 100644
--- a/lib/rubygems/config_file.rb
+++ b/lib/rubygems/config_file.rb
@@ -337,7 +337,7 @@ if you believe they were disclosed to a third party.
       end
       return content
     rescue *YAMLErrors => e
-      warn "Failed to load #{filename}, #{e.to_s}"
+      warn "Failed to load #{filename}, #{e}"
     rescue Errno::EACCES
       warn "Failed to load #{filename} due to permissions problem."
     end
diff --git a/lib/uri/common.rb b/lib/uri/common.rb
index 00051a8..facca4b 100644
--- a/lib/uri/common.rb
+++ b/lib/uri/common.rb
@@ -51,7 +51,7 @@ module URI
         end
       else
         raise ArgumentError,
-          "expected Array of or Hash of components of #{klass.to_s} (#{klass.component[1..-1].join(', ')})"
+          "expected Array of or Hash of components of #{klass} (#{klass.component[1..-1].join(', ')})"
       end
       tmp[:scheme] = klass.to_s.sub(/\A.*::/, '').downcase