diff --git a/ChangeLog b/ChangeLog
index b80aa2d76f..3d2411f68c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Fri Mar 11 01:40:35 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* process.c (proc_getmaxgroups, proc_setmaxgroups): Process#maxgroups
+	  and Process#maxgroups= now raise NotImplementedError if the
+	  platform don't support supplementary groups concept.
+
 Fri Mar 11 01:25:03 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* process.c (get_sc_ngroups_max): return -1 if platform don't
diff --git a/NEWS b/NEWS
index b6a49d3ea9..fca7558321 100644
--- a/NEWS
+++ b/NEWS
@@ -80,6 +80,10 @@ with all sufficient information, see the ChangeLog file.
     * extended method:
       * Time#strftime supports %:z and %::z.
 
+  * Process
+    * Process#maxgroups and Process#maxgroups= now raise NotImplementedError if
+      the platform don't support supplementary groups concept.
+  
 * io/console
   * new methods:
     * IO#noecho {|io| }
diff --git a/process.c b/process.c
index f3138afa80..24e7bf9162 100644
--- a/process.c
+++ b/process.c
@@ -4524,6 +4524,7 @@ proc_setgid(VALUE obj, VALUE id)
 #endif
 
 
+#if defined(HAVE_SETGROUPS) || defined(HAVE_GETGROUPS)
 /*
  * Maximum supplementary groups are platform dependent.
  * FWIW, 65536 is enough big for our supported OSs.
@@ -4566,6 +4567,7 @@ static int maxgroups(void)
 
     return _maxgroups;
 }
+#endif
 
 
 
@@ -4719,7 +4721,7 @@ proc_initgroups(VALUE obj, VALUE uname, VALUE base_grp)
 #define proc_initgroups rb_f_notimplement
 #endif
 
-
+#if defined(_SC_NGROUPS_MAX) || defined(NGROUPS_MAX)
 /*
  *  call-seq:
  *     Process.maxgroups   -> fixnum
@@ -4735,8 +4737,11 @@ proc_getmaxgroups(VALUE obj)
 {
     return INT2FIX(maxgroups());
 }
+#else
+#define proc_getmaxgroups rb_f_notimplement
+#endif
 
-
+#ifdef HAVE_SETGROUPS
 /*
  *  call-seq:
  *     Process.maxgroups= fixnum   -> fixnum
@@ -4764,6 +4769,9 @@ proc_setmaxgroups(VALUE obj, VALUE val)
 
     return INT2FIX(_maxgroups);
 }
+#else
+#define proc_setmaxgroups rb_f_notimplement
+#endif
 
 #if defined(HAVE_DAEMON) || (defined(HAVE_FORK) && defined(HAVE_SETSID))
 #ifndef HAVE_DAEMON
diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index f3f3f9eb80..39c8b18966 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -1158,6 +1158,7 @@ class TestProcess < Test::Unit::TestCase
 
   def test_maxgroups
     assert_kind_of(Integer, Process.maxgroups)
+  rescue NotImplementedError
   end
 
   def test_geteuid