diff --git a/ChangeLog b/ChangeLog
index c87146519c..42548dc844 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 Fri Jan 13 03:46:53 2012  Akinori MUSHA  <knu@iDaemons.org>
 
+	* lib/shellwords.rb (Shellwords#shellescape): shellescape() now
+	  stringifies the given object using to_s.
+
+	* lib/shellwords.rb (Shellwords#shelljoin): shelljoin() accepts
+	  non-string objects in the given array, each of which is
+	  stringified using to_s.
+
 	* lib/shellwords.rb: Fix rdoc markups.
 
 Fri Jan 13 03:38:36 2012  Akinori MUSHA  <knu@iDaemons.org>
diff --git a/NEWS b/NEWS
index 58370a6a28..32480e014f 100644
--- a/NEWS
+++ b/NEWS
@@ -55,6 +55,11 @@ with all sufficient information, see the ChangeLog file.
     * Resolv::DNS#timeouts=
     * Resolv::DNS::Config#timeouts=
 
+* shellwords
+    * Shellwords#shellescape() now stringifies the given object using to_s.
+    * Shellwords#shelljoin() accepts non-string objects in the given
+      array, each of which is stringified using to_s.
+
 === Language changes
 === Compatibility issues (excluding feature bug fixes)
 
diff --git a/lib/shellwords.rb b/lib/shellwords.rb
index 550c2693de..2aaa30c23c 100644
--- a/lib/shellwords.rb
+++ b/lib/shellwords.rb
@@ -57,7 +57,8 @@ module Shellwords
   end
 
   # Escapes a string so that it can be safely used in a Bourne shell
-  # command line.
+  # command line.  +str+ can be a non-string object that responds to
+  # +to_s+.
   #
   # Note that a resulted string should be used unquoted and is not
   # intended for use in double quotes nor in single quotes.
@@ -77,6 +78,8 @@ module Shellwords
   # Multibyte characters are treated as multibyte characters, not
   # bytes.
   def shellescape(str)
+    str = str.to_s
+
     # An empty argument will be skipped, so return empty quotes.
     return "''" if str.empty?
 
@@ -101,7 +104,9 @@ module Shellwords
   end
 
   # Builds a command line string from an argument list +array+ joining
-  # all elements escaped for Bourne shell and separated by a space.
+  # all elements escaped for Bourne shell into a single string with
+  # fields separated by a space, where each element is stringified
+  # using +to_s+.
   #
   #   open('|' + Shellwords.join(['grep', pattern, *files])) { |pipe|
   #     # ...
@@ -113,6 +118,11 @@ module Shellwords
   #     # ...
   #   }
   #
+  # It is allowed to mix non-string objects in the elements as allowed
+  # in Array#join.
+  #
+  #   output = `#{['ps', '-p', $$].shelljoin}`
+  #
   def shelljoin(array)
     array.map { |arg| shellescape(arg) }.join(' ')
   end